Error while reading PP/DS alerts (SAP liveCache not available)

What causes this issue?

The system was unable to access the SAP liveCache when determining the
PP/DS alerts.

System Response

The system cannot determine any PP/DS alerts.

How to fix this error?

Ensure that the SAP liveCache is available.
Then reinvoke the Alert Monitor.

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.