We have also run into this error, it occurs on Windows 10 v1903 and above. v1809 seems to work fine. The new version of CWW, 6.3.x is also broken on Win10 19xx, but the message looks like this:
We've tried IE, Chrome, Firefox, Opera, Edge, new Chromium Edge, no go on any of them. The problem seems to be in IIS, but nothing tweaked in there has helped either. We have a pc on Windows 10 version 1809 that's kept off the internet so it won't auto update, and run it like that.
I am also having this issue. We have about 45 Xereox printers and really want to use this management tool. Installed on a brand new VM Windows 2012 R2 server. Tried to contact Xereox support, but they refuse to help since our machines are leased through a 3rd party.
Have you tried using a different browser to see if you still get the error? I searched the Forums and found this post with a similar issue, there may be something in here that will help you:
This is a second time I have come accross this issue but no one was able to help me with it. This time, this is a fresh new instance of CWW on Windows 10. Could someone please point me the right direction? Thank you.