UNEXPECTED ERROR prevents starting any game

[Slippersfordad]

I'm getting a red banded error message every time I try to start a game:
UNEXPECTED ERROR - YOU MUST ACCEPT PLAYERSAT YOUR OWN LEVEL (GOOD PLAYERS)
I don't know what this came from or how to get it to go away or re-set.
Can anyone help???

[euklid314]

The message sounds as if you tried to create a game while restricting access to this game.

If you are ELO-wise a good player yourself you cannot restrict the game only to, e.g., expert players. If you want to exclude weaker opponents you at least have to allow your opponents to be your own ELO strength and better...

I hope that my information is correct - I am quite sure but not 100%.