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For what it is worth, whenever I see that message, it is always related to a permission/login issue - especially if I have logged in as another user and left my admin portal open in the same browser. You can only have one user open at a time in same browser, and it messes with permissions when doing what I suggested. In these cases, I have to log out of my lower permission user and then get out of my admin portal and log back in. That fixes the request cannot be completed at this time error - every time. I don't know if your scenario is anything like that, but throwing it out there just in case.

I did when I tried to make a change to a group.  Finally gave up after a day and opened a ticket w/Support and they determined I had to re-build group from scratch, which I did, and it fixed it.  They did not say what caused it.