Can't Add User to Security Group in 26.06

Summary:

I can't seem to add users to security groups in 26.06 via the "Manage Users" tab of the "Access Control" pages. None of the security groups appear in the "Available" groups section. I tried searching for specific groups with no luck. I was still able to add users to security groups via the "Manage Groups" tab as a workaround. Is anyone else encountering this issue?

Version (include the version you are using, if applicable):

26.06