SSAS 2022 Connections fail following restart

I'm using an application which has SSAS 2022 OLAP cubes at the back end.

We are having an issue that whenever we restart the server or the service, the connections to the SQL Server that is the data source break. 

I suspect this is a consequence of SSAS CU1 behaviour where the connection string is encrypted, but - because they get encrypted - there's no way to identify what the change is. 

SSAS is on the same instance as the SQL Server. 

Before a restart, i've tried adjusting a few connection properties, notably

• Impersonation set to Service Account
• Trust Server Certifcate to True
• Encryption for data to Optional

The connection works fine with these settings. However, post reboot I get a connection error whenver I try toprocess any objects:

Errors in the back-end database access module. No provider was specified for the data source.

We are using MSOLEDB19 so should be fine, but it seems that post reboot the encrypted connection is somehow misconfiguring. 

Appreciate any guidance on what could be happening here? I can't avoid restarting the server as org policy demands servers are rebooted every fortnight.