Outline Agreement Number in Source List

Hello,

I've a Source List that has an entry for a given meterial and vendor combination for a particular period with an outline agreement number. I get an error stating "Source not included in list despite source list requirement" when I raise PR for the same material and vendor combination. The plant in Source List as well as PR is the same. Can you please explain why I'm getting this error even though the source is maintained in the source list? I'm not getting this anymore if I put another entry in source list for the given material, plant and vendor combination without outline agreement number.

Thanks,

Sankar