I just noticed I am getting this error, too.
The last time this happened it was broken at their end, and everyone here kept saying things like “clear browser cache, private tab, other browser”, etc. None of that helped back then, either. It didn’t start working until some group inside Samsung fixed the back end.
That this can repeatedly happen… and not be immediately resolved (and fixed to never happen again)… is an example of what SmartThings has devolved into.