Microsoft Remote Access black screen via MacBook Air

I have a MacBook Air, currently on Ventura 13.3. For the past 2 years I have successfully used the Mac to remote access my work windows via Microsoft Remote Desktop. Earlier this year, following a WiFi setting change from router to modem (virgin) I find that I can no longer use remote access effectively. I try to log in as normal via WiFi and the remote access is enabled but I only see a black screen with an arrow. However when I try to log in again via my hotspot, it works fine.

is anyone able to assist with where the issue lies? Work iT department have not had any success and think it is a firewall issue?!