This was happening to me a year ago but it did get resolved for me. I am currently able to log in and control devices using a few different browsers.
https://fwd4.mios.com/remote/1.5.622-en/?PK_AccessPoint=xxxx&token=xxxx
I’m running the same firmware 1.5.622 but I guess I’m directed to a different server? (fwd4). I tried changing 4 to 3 and saw the message you got.
At this point I’m reluctant to change anything for fear of breaking it. You should probably file a ticket with support though I’m not sure how much time they are willing to put into these legacy systems.
Check this note from last year…
Good Luck…
Rich