Sage CRM 2019 R1 Sage 300 integration not working

I have a client that's upgrading from Sage CRM 2017 and Sage 300 2017 to Sage CRM 2019 R1 and Sage 300 2019 PU2.

This install was working fine the other day. The only thing that was changed that I know of was the password for the CRM user 'CRM'.

Lately, when I open a company in CRM who is a customer in Sage 300 and I go to the 'Customer' screen in CRM I get the following message:

'You are not authorized to complete this task. Contact your system administrator for help.'

Did the password change cause this or is there something else going on?

As always, any and all advice greatly appreciated,

Dana