Forum Discussion
Modern teamsites - unable to change permission level for security groups
I am able to partly reproduce your behavior in my tenant, only for the first part in which the buttons remain greyed out for the default created Groups. When I grant permissions using leftmost Grant Permissions button I am able to use both buttons afterwards
I don't know exactly why this is, but I can imagine it's to protect you from messing up the permissions with regards to the underlying O365 Group that's created for modern team sites and keep the basic permissions model controlled through O365 Group settings working.
paulpascha I found that despite being an Administrator and an Owner for a site, I was unable to change permission levels for a security group after Microsoft had assigned the "limited access" permission level to the Owners or Members security groups (of which I was a member). The "limited access" permission level is apparently assigned when a user shares a document/list with someone who is already a member of the Sharepoint Site (LOTS of Sharepoint/Microsoft community blogs and complaints about this). The problem is you cannot delete the Limited Access permission level and you cannot remove the Limited Access for the security groups to which assigned (greyed out).
The way I got around this is to create two Custom security groups (CustomOwner and CustomMember with the required permission levels) .... and added the applicable staff/O365 Groups with these custom groups. Not sure whether that horrid "limited access" will pitch up again for the custom security groups if an item/document is shared; I am too nervous to test after so many hours researching these issues
