Unable to see Azure Security Group to assign to Purview Labelling Policy - Information Protection

Hello - When navigating within the Purview Portal to add a "dynamic" Azure Security group to an existing labelling policy the security group is not appearing in the pick list. The informational banner details

"The labels you selected will be available for the users, distribution groups, mail-enabled security groups, and Microsoft 365 Groups you choose here.​" 

I do not want to have to create a whole new group to add all staff given we have internal AD groups already available. Please advise.

ps: I also elevated my account to 'Compliance Administrator' and confirmed the security groups is still not visible.