Error Message when trying to add an Alternative Host to meeting

[vshapland]

I am trying to add a colleague (same organization, same Zoom license) as an alternative host for a meeting but I keep receiving this error message:

"Unable to assign "***********" as an alternative host because the user cannot be selected at this time"

No reason for why they can't be added, just this error message. Would love any solutions or suggestions folks have to offer!