Program & cannot run at the moment due to the sequence number

What causes this issue?

Program & cannot run at this point because not all programs whose
sequence number is lower than the one for program &1 have been
completed successfully.

System Response

The program was stopoed.

How to fix this error?

Wait until all programs whose sequence number is lower than the one for
program &1 are completed, then schedule a new job in the
conversion 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.