1) SCOM 2019 has only just been installed. It is monitoring only 10 servers. The initial database size is hundreds of Gigs.
2) OM is at the latest CU
3) I am a full administrator
Other interesting things of note:
I launch the new group wizard
I enter a name and proceed to the dynamic members bit
I press create/edit rules
I insert an expression
I click the property drop down and its empty - no idea why
I delete the expression I just inserted
I then press the add button next to the Windows Computer class and this time the property dropdown shows a list of properties
I delete what I just added and go back to inserting an expression - now the property dropdown is populated????
When I try to use the netbios name criteria it fails as explained above