Try to send him a message by email.
https://app.audiogon.com/users/robben/feedbacks
https://app.audiogon.com/users/robben/feedbacks
Left hand side of page, "Send message".
.
https://app.audiogon.com/users/robben/feedbacks
https://app.audiogon.com/users/robben/feedbacks
Left hand side of page, "Send message".
.