Error in RFC & to Solution Manager System

What causes this issue?

The Remote Function Call (RFC) to the SAP Solution Manager system could
not be made because of the cross-system object lock settings.
This may be because:
No connection can be established to the RFC destination &V1& in the SAP
Solution Manager system.
The RFC destination user is not authorized to use the SAP Solution
Manager system.
The RFC destination user is neither a service nor a dialog user of the
SAP Solution Manager system. The system shows no conflict dialog box.
Other exceptions have occurred.

System Response

Processing canceled.

How to fix this error?

Ask the system administrator to take one of the following measures:
Determine the cause and solution of the problem.
Perform Customizing activity <ZK>Configure and Activate Cross-System
Lock</>, to specify a service user.
If the error remains, contact SAP support.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.