Cannot access contents of request &1 in system &2

What causes this issue?

The system could not read the spool request data.

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?

Notify your system administrator.

Procedure for System Administrators

Check the consistency of the spool database. You may find more
information about the cause of the error in the system log.

Error message extract from SAP system. Copyright SAP SE.