Xero User Permission Settings
Here are the minimum permissions in Xero that a user needs to have to be able to use Xero and MagManager.
If the users does not have the Xero user permissions set up correctly in their Xero account, they will likely see the following screens appear when they try to access a client record:
MagManger User Settings To Work with Xero
In MagManager their user settings should be either set to Admin or if they are not an admin MM user the Can Use Xero option should be ticked.