Output could not be issued.

What causes this issue?

An error occurred while <GL:output>output</> was being issued. It is
possible, for example, that the <GL:form>form</> to be issued has not
been activated or has an error. An error may also have arisen while the
data to be issued was being edited.

How to fix this error?

Check possible causes of the problem.

Error message extract from SAP system. Copyright SAP SE.