Cannot access server "&1": &2&3&4

What causes this issue?

The server with the name "&V1&" is part of this system.
This server cannot be reached by RFC to check there whether the secure
storage in the file system of that server can see the current encryption
key set in this server.
The error message is:
&V1&&V2&&V3&

System Response

It is not possible to re-encrypt entries with the current encryption
key, since this precheck is intended to prevent entries being updated to
an encryption key that cannot be read system-wide.

How to fix this error?

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

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.