Error generating release against scheduling agreement & (cause &)

What causes this issue?

The function module for generating a scheduling agreement release
(forecast delivery schedule or JIT delivery schedule) has run up against
an error, causing processing to be terminated.
In this case the cause of the error is &v2&.

System Response

The error may involve one of the following situations:
<ZH>1:</> The nature of the error cannot be specified precisely.
<ZH>2:</> The forecast delivery schedule or the JIT delivery schedule
was generated but no message record could be generated.
<ZH>3:</> A document type for which the functions "Generate forecast
delivery schedule" or "Generate JIT delivery schedule" are not defined
may be involved.
<ZH>4:</> A material for which the function "Generate JIT delivery
schedule" is not defined may be involved.
<ZH>5:</> A scheduling agreement that has not yet been released by all
persons responsible may be involved.
<ZH>6:</> The factory calendar has not been maintained correctly.

How to fix this error?

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

Error source <ZH>1</>:
Check whether the supplier and plant shown in the PO actually exist in
the system.
Error source <ZH>2</>:
Check the Customizing facility for message determination with respect to
delivery schedules created under scheduling agreements (print operation
'9').
Error source <ZH>3</>:
In Customizing, maintain the document types accordingly (
<DS:SIMG.SIMG_CFMENUOLMEOMED>Define document types for scheduling
agreement</>). Then create a new scheduling agreement with a document
type for which release documentation is defined.
Error source <ZH>4</>:
Maintain the JIT delivery schedule indicator in the material master
record.
Error source <ZH>5</>:
Have the scheduling agreement released by the person(s) responsible.
Error source <ZH>6</>:
If you are using a
<DS:GLOS.3526C099AFAB52B9E10000009B38F974>release creation profile</>
without aggregation, you must maintain the factory calendar for the next
999 days.
IMG -> General Settings -> Maintain Calendar

Error message extract from SAP system. Copyright SAP SE.