Error when reading client table in system &1

What causes this issue?

The client table is read when the client list is adjusted with the SAP
system &V1&. During this there was an error.

System Response

You are only permitted to maintain the recognized clients. The client
000 is always available.

How to fix this error?

Check the error using the TMS messages.

Procedure for System Administrators

Possible errors:
Network problems
Non-running SAP system

Error message extract from SAP system. Copyright SAP SE.