Why would balanced loading stop assigning to a user?

[Ada Skillings]

I have an automation to assign new tickets to users in a group. One of the users in that group has not been assigned new tasks for almost a week now.

I have confirmed that he is in the group, and removed and add him back in.

His queue is smaller than the rest of the team, so it should not be choosing to not assign to him due to a high number of tickets.

What other possible causes for this are there?