It could be that Cisco firewall at the customer site is somehow blocking this even though 8.5 2021-11-02 (build 85420021) had no problems.
They have a web proxy too.
I have tested with 2022-09-20 version and it worked for a few minutes and then stopped responding to key presses (Enter, Ctrl+Enter)
CPU usage for idle SERP client is up to 10%, while on my test installation with the same build is 0,5% or so.