No source list entry exists for material &1 in plant &2

What causes this issue?

You have not specified a vendor in the JIT control cycle for material
&v1& in plant &v2&. The system now automatically searches for a source
list entry for the material and the plant. However, no valid entry has
been found.

System Response

The system has terminated the process and has not created a JIT call.

How to fix this error?

You can make an entry in the source list via <DS:TRAN.ME01>Maintain
Source List</>. You can also generate source list entries automatically
via the <DS:TRAN.ME05>Generate Source List Entries</> function.

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.