Create user fails in v9.0.3.7 on prem

Hi all,

I'm getting an error when I try to add a user in Dynamics 365 Customer Engagement v9.0.3.7 on premise and the error I'm getting is this: "<Message>Assembly Microsoft.Dynamics.Service.Plugins.dll can not be loaded.</Message>"

Has anyone else seen this and have any ideas of how to fix it?

Oh, and the version list below is inaccurate :)

Regards