Hello
We recently implemented a change which prevents use of Domain local or Distribution groups for Role use. Could it be the group you are using is a Domain local? This would have continued to work, if so, despite us no longer allowing these type of groups to be selected when chosing to add as a member to the role, up until a few days ago.
Please check the group you are referring to and if a domain local or a distribution group, please convert it.
This KB not only explains the changes, why and when they were made, but also how to correct it.
Please let me know if this does not help, and we may need to dig deeper (perhaps open a Support case if possible?)
I hope this is a qucik fix for you.
Have a great weekend!!
Ryan V.