Thanks for your feedback.
Please do the follow and please upload the latest log files. Thanks for your corporation!
1>please double check there is a role name _memeber_
2> please try to add a group to a project in horizon
3> after it failed, please collect the latest log by run viogetlogs
Since by the last log files we are pretty sure it was caused by missing the _memeber_ role.
with the latest log after the _member_ role created will help us to identify the issue why you still can't assign a group to a project.