Wait for Scheduler

What causes this issue?

The bgRFC cannot process this message for some reasons (i.e. not enough
system resources or wrong configuration).

System Response

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

How to fix this error?

Ask your system administrators to check the bgRFC configuration
(transaction SBGRFCCONF) and also the system resources (Dialog work
processes).

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.