I can't be the only Cary Audio DMS-600 user experiencing this problem streaming Qobuz ...

The problem still exists.  Everything you have mentioned has been recommended by the engineers at Cary Audio.  The latest is I removed the apps from my 2 controllers, I completely reset my router/modem/gateway; Zyxel Model # EMG3415-B10A, my 16 port gigabit switch, and my access point.  I then went into my DMS-600 and reset the network settings, then performed a factory rest.  Unplugged the unit after boot up for 5 minutes.  Replugged in and waited 2 minutes to power up.  Then only reinstalled the Cary App on my I-Phone 8 as it has the latest software version at 14.5.1.  Everything played fine for 2 days and then on the 3rd day Tidal stopped after 32 minutes and then stopped another hour later. 

The Cary Engineers performed their test on a DMS-600 with my log in information to Spotify and did not experience any problems.  My problem is primarily with Tidal.
So where does that leave me.  Cary sells their products direct in the US so I have to deal with the Sales Manager directly.  He found a Technical support article on the Cambridge Audio website which suggests establishing a Static IP address specifically for the DMS-600 to the Cloudflare public DNS server.  This is offered only as a suggestion and not a confirmed resolution.
My problem is I am having a problem finding an IT guy to help me test this change in my ISP's supplied Gateway/Router/Modem.  It can be done, but the Cincinnati Bell Service Technician that came out last week does not know how to do it.  My AV dealer wants me to purchase a new Luxul XWR3150 router for $425 and then just use the ISP Zyxel unit as a modem.  They would do the installation and set up, but they are not guaranteeing me a resolution with Tidal either.
If anyone has experience with the Zyxel EMG3415-B10A unit and can help me, please reply.  I have gone through the 200 page owner's manual multiple times, and while I am getting close, I am still stumped in one key area of where to input the CloudFlare information.  I have the admin password and can make the changes to my current unit, but the way the information is displayed, it is not as easy to follow as on some other routers.
The suggested solution is by going through a public DNS server, it will be quicker than the ISP servers and the information packets from Tidal would be processed quicker.  Tidal plays fine on my Sonos S2 app, so I still think it is the Cary 2.0 app.  I asked is upgrading to the DMS-700 would help, or if DMS-700 customers were having this problem, but was told by the Sales Manager that he did not feel upgrading would help in my situation.  He never really answered my questions.  All I can still say is I had no problems whatsoever for 3 years until Cary changed to the 2.0 Streamer App.

This makes no sense. You said “Everything played fine for 2 days and then on the 3rd day Tidal stopped after 32 minutes and then stopped another hour later”. Why does it play perfectly for 2 days and then stop on the next day?

Since it worked on the previous version, and not the Cary 2.0 App, implies the issue is with the 2.0 version. However, since it worked for 2 days, and then not work the next is a concern. When software works, it ‘usually’ works all the time and not for 2 days and then not. I have no clue what could be causing this. I am also surprised that Cary cannot help solve the issue.

Is it possible your router sometimes has failures that is causing the issue? Can you borrow another router and test it? BTW, several years ago, I was using an Apple Extreme router that sometimes had streaming issues. I replaced it with a Luxul 3100 router and everything worked.

I am not a fan of using the suggested solution of going through a public DNS server.

I hope someone else can solve this issue. Help?

Is it possible you are having Router intermittent connection drops?  I found these suggestions by searching the Internet. 

“Random disconnect problems are generally hard to pin down because there are so many variables to consider in both your ISP’s network and the router you use. The main way to attack the problem is with good old disciplined troubleshooting techniques and lots of patience. We don’t have a sure-fire fix for you, but these troubleshooting tips should help:

1. As much as it’s a pain, get the router out of the loop and see if you have the problem with just one computer attached directly to the Cable or DSL modem. If you still have the problem, at least you’ll only get the run-around from your ISP!
2. If the problem goes away without the router, reconnect the router and upgrade your firmware to the latest revision. This is usually available from the router manufacturer’s support website.
3. While you have a normal connection, log into the router admin pages, and take a screen shot of the Status page, or at least write down the WAN IP, Gateway, and Primary and Secondary DNSinformation. Save this in a handy place next to the router”.

Please also check to see if your router firmware needs to be updated. Please keep us posted.

NOTE: I like the above suggestion to bypass the router and see what happen.

After some more thought, I strongly suggest you connect your Cary Audio DMS-600 direct to your modem and bypass your router.

Please also check to see if your router firmware needs to be updated.

This test will either confirm your router is working okay OR is the cause of your Tidal streaming dropouts.

If the router proves to be okay, you probably need to look at the Carry 2.0 App.

Please keep us posted. Thanks.

Thank you for your suggestions.  The Zxyel EMG3415-B10A is a combination modem/router/gateway provided by Cincinnati Bell Fioptics. My connection is fine.  If I was having dropouts it would affect all of my connections throughout my home and that is not the case.  The Fioptics technician was more than willing to give me a new Zxyel unit, but since I have an isolated problem with only one piece of equipment, it was determined that replacing this unit would not solve my problem.  To reiterate, I have no dropouts when streaming music from my other receivers/devices throughout my home.  That includes streaming Tidal from my Sonos S2 app.
But complaining is not solving the problem so through my local A/V dealer, I have ordered the XWR-3150 Luxul router, and a new Luxul XGS-1024S 24 port gigabit switch.  We will only use the Zxyel unit as a modem.  The Luxul router will control everything else.  In addition to installing these new devices, signal strength measurements will be taken throughout my home and I might add an additional access point in my lower level where my stereo is located to enhance my already acceptable wireless signal.  I already employ a Luxul XAP-1510 access point in the center of my main floor.  Over 2 floors, I am covering approx. 4,000 square feet. 

My whole house is hardwired for ethernet so I am only using a couple of ancillary devices as controllers for the Sonos and Cary apps.  At the suggestion of Cary Audio, I even removed the 2 Wi-fi antennas from the DMS-600 and only use Bluetooth..
So hopefully within the next month when the A/V technician becomes available, I will enhance my Ethernet and Wi-fi coverage throughout my home.  If spending over $1,000 to address this problem does not solve it, at least I will have a better internet/Wi-fi experience moving forward and it will provide me with new ammunition to go back to Cary Audio and tell them they have a problem with their 2.0 streaming app.  No more excuses from Cary as I have addressed what they consider to be a network problem on my end.  Of course none of these manufacturers ever accept responsibility for anything.  It is always the customer's fault.  Well I am putting my money where my mouth is and I will hope for the best.  I will provide an update in the future. Thank you for your continued interest and help.
One last comment:  When I perform a factory reset on the DMS-600, I cannot figure out why it works fine for a day or two and then keeps stopping periodically.  When streaming Tidal, my streamer continues to stop after the first 30 minutes and then another hour later and so on.  This has occurred every time I stream Tidal from this unit since the last reset.  Spotify and internet radio is not affected. Sure doesn't seem like a network issue to me.  Cary wants me try a static address for CloudFlare's public DNS server and that is what I am going to do.  I can always change it back to DHCP.