Document type &1 not allowed with doc. category &2 (Please check input)

What causes this issue?

The <DS:GLOS.3526BFD0AFAB52B9E10000009B38F974>document type</> <ZH>&V1&
</> you entered is not allowed in combination with the
<DS:GLOS.3526BFD1AFAB52B9E10000009B38F974>document category</> <ZH>&V2&
</>.
The combination of document type and document category entered cannot
be used because it has not been defined in Customizing for
<ZK>Purchasing</>.
The following (internal) document categories exist:
B - purchase requisition
F - purchase order (PO)
K - contract
L - scheduling agreement
A - request for quotation (RFQ)
<ZH>Example</>
You cannot create a PO (document category <ZH>F</>) with the document
type <ZH>scheduling agreement with release documentation</> (LPA).

How to fix this error?

INCLUDE EINGABE_PRUEFEN_NA LANGUAGE EN
INCLUDE SYSADMIN_NA LANGUAGE EN
DEFINE &OBJEKTE& = 'The document types/categories'
INCLUDE NA_EINK_CUST LANGUAGE EN

Error message extract from SAP system. Copyright SAP SE.