A co-worker and I have been experiencing these same faults, and found a way around them for now. I decided to write this up in case it's helpful for anyone else.
The root problem is on RS 2021.2, on robots running RW 6.12. RS is running on WIndows 10 computers, using DHCP and One-Click Connect through the Management port on the front of the IRC5.
Now, for days we were able to connect to these robots this way, and perform RAPID edits and controller and I/O changes without any issues. However, after we started opening the SafeMove configuration, things changed. Now, RS began asking for login credentials immediately upon connection, where it had never requested them before. Even after a complete reboot, RS would demand login immediately.
We had login credentials already set up (with full grants for everything), but when we used them, RS would throw "RobAPI" Faults, and "unable to read configuration from controller". The FlexPendant Viewer would just show a blank screen, the SafeMove configuration would not load from the robot, and Request Write Access was greyed out, showing a pop-up message that we lacked the correct grants to even request write access.
The maddening thing was, this wasn't consistent -- sometimes everything would work as intended, then, if we switched to a different robot, or restarted RS, we'd be back to this problem.
The workaround we found that seems to be reliable (so far) is to first login as Default User, then use Authenticate>Login As Different User to "upgrade" ourselves to full "admin" grants. This has allowed us to get by, and make SafeMove edits.
I've not encountered this behavior on any IRC5 before. My most recent previous experience was on IRC5s running RW 6.10, with RS 2019.
One thing I've noticed: Once I've followed the workaround procedure once, the "fix" appears to be persistent, as long as I stay connected to the same robot. If I close and restart RS, I won't get a Login prompt on connect, and RS throws no faults. If I reboot my computer, however, I have to start all over again.
