Supplier &1 is not an allowed source of supply

What causes this issue?

In the source of supply check it was determined that vendor &V1& is not
a valid source of supply for material &V2&.

System Response

Prices could not be calculated for material &V2&.

How to fix this error?

Check the purchasing info record for material &V2& and vendor &V1&. The
system may have refused the vendor as a source of supply because the
vendor is unable to deliver in the validity period of the price
calculation.

Error message extract from SAP system. Copyright SAP SE.