And that confirm you have admin rights?
You mentioned that you ran into a similar problem of not being able to access a group before and had to delete it
Were you able to identify a possible cause? If you can share details on how the group was configured and if okay the name of the group. May help with troubleshooting.
You may need to delete the group as per how you did last time. Then try to recreate the group and detail steps to see if this occurs again with the group your trying to create.