Multiple Roles

Hi,
Originally when we installed the plugin we were able to assign multiple roles to each user.
However, now when adding a new user we are unable to assign more than one role, we only have the default drop-down option instead of the multiple tickbox field. I’ve updated the plugin to the latest version, disabled all other plugins and switched to the Twenty Twenty Two theme but this hasn’t helped.

Can you guide me on how to debug this further?

Thanks
Andrew