Remote Desktop Error 0x204 on Virgin WiFi

Hi there,

As the title suggests, I'm getting this error message: 0x204 from Remote Desktop. It's only happening when we are connected to our VM WiFi. It's just started recently and has worked fine for about 2 years prior to this.

I've tried connected to RDP through a desktop PC and a Laptop, both producing the error message and both working when we swap to a mobile hotspot. I've gone through about every firewall setting I can find through advice online and disabled/enabled countless settings but no luck. I tried the VM phone helpline too which was useless as they were just sending me in circles, handing off the call to other agents.

Has anybody faced this issue with VM WiFi and had a fix? Remote desktop is vital for our jobs and it is currently only working on a mobile hotspot (any we don't have endless data). Really don't want to have to switch provider just for one app but it's vital.