O365 Groups or Unified Groups is a cool O365 feature, except when it don’t work as expected.
You just deleted the Group, but the hidden SharePoint Online Site Collection connected to the group didn’t got deleted automatically with the group.
Guess what it’s now an orphaned site collection in locked state.
To Remove these sites, follow the script below:
##Connect to SPO
Connect-SPOService -Url https://tenant-admin.sharepoint.com
#Get all SPO Sites | find your orphaned O365 Group Site Collection
#The SPO site Collection is actually locked, unlock it
Set-SPOSite -Identity https://tenant.sharepoint.com/sites/site -LockState Unlock
#Then remove the orphaned site
Remove-SPOSite -Identity https://tenant.sharepoint.com/sites/sites -NoWait
FIX THIS MICROSOFT!!