Tweeter absolutely silent. What could be the reason?

I have had same problem before. If you can, take the tweeter
driver out of cabinet and measure by omhs. If your speaker
range in 8 ohms-the tweeter must be in the range from 6 to
8 ohms...If your tweeter drive in that range, replace the
cross over pcb.

Easier to check for an open voice-coil by touching a 1.5v battery to the terminals and listening for scratchy sounds.
Tweeters are pretty go-nogo devices. Their sensitivities unfortunately vary dramatically within most production schemes, so don't be surprised if a replacement tweeter results in a change in spectral tilt, necessitating a resistance pad on EITHER of the resultant pair to reach equivalence. It can be a pain.... Good luck.

Abbe Lowell is the advising counsel?