Invoice document & cannot be processed further

What causes this issue?

The invoice document &V1& contains the purchasing document &V2&, and the
item &V3&. You cannot enter the invoice for this item, or you cannot
cancel this invoice document. There can be several possible causes, for
example:
- the PO item is blocked
- the PO item is flagged for deletion
- another colleague is currently processing the purchase order
- the purchase order has not yet been released
- the corresponding service entry sheet has been deleted
- for a held invoice against planned delivery costs: the supplier in the
held invoice is not the same as the supplier in the condition in the
purchase order, or the same as the supplier from the purchase order
history entries. This is due to the fact that the supplier in the
condition in the purchase order has been changed in the meantime. In
this case, the held document cannot be processed further. You can use
report Z_MRM_DELETE_PP from note 501905 to delete the document.

System Response

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

How to fix this error?

Check the purchase order.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.