Changes to the cross-client Customizing are not permitted

What causes this issue?

There is a rule preventing changes from being made to cross-client
Customizing. This rule applies either to the entire system or just to
the client.

System Response

It is not possible to make changes to operating concern "&V1&".

How to fix this error?

If you want to make changes to operating concern "&V1&", you need to
change the settings for the client. Either
Choose <LS>Administration -> Management -> Client Administration ->
Client Maintenance</>, or
Use the global system change option (transaction SE06).
In the client, it must be possible to make changes in Customizing for
cross-client objects.
In the global settings for the system change option, it must be
possible to make changes to client-specific Customizing.

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.