Item for reference &1 &2 &3 &4 not permitted

What causes this issue?

<ZH>No invoice documents</> have been entered for this purchase order
item yet.The following invoice document categories (transactions) can be
entered:
<LS>Invoice</>
<LS>Credit memo</>
<LS>Subsequent debit</>
<LS>Subsequent credit</>
IF &[SWITCH]MM_SFWS_DINV_02& = 'X'.
<LS>provisional invoice/differential invoice</>
ELSE.
<LS>Provisional invoice</>
ENDIF.
<LS>Final invoice</>

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

An invoice document has <ZH>already</> been posted for this purchase
order item. Depending on the preceding document, different follow-on
documents (transaction categories) are possible.
For the preceding documents <LS>Invoice</>, <LS>Credit Memo</>, <LS>
Subsequent Debit</>, or <LS>Subsequent Credit</>:
<LS>Invoice</>
<LS>Credit memo</>
<LS>Subsequent debit</>
<LS>Subsequent credit</>
IF &[SWITCH]MM_SFWS_DINV_02& = 'X'.
For the preceding document <LS>Provisional/Differential Invoice</>
<LS>Provisional invoice/differential invoice</>
<LS>Final Invoice</>
ELSE.
For the preceding documents <LS>Provisional Invoice</> or <LS>
Differential Invoice</>:
<LS>Differential invoice</>
<LS>Final Invoice</>
ENDIF.
For the preceding document <LS>Final Invoice</>:
<LS>Subsequent debit</>
<LS>Subsequent credit</>

System Response

How to fix this error?

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.