Hi,

Apps version : 0.17.8
Nextcloud version : 17.0.0

I tried 3 ways :

1. param Maximum member to 0
2. param Maximum member to -1
3. param Maximum member to 100

For 1 & 2, I obtained the error :
Group contains too many members

For 3 the group added.

For information, the param by default (admin) for Max member is 300 and the groups contain 1 to 3 members for now.

Sorry for my english.