Identifying PO can't edit and not getting values there

Summary:

While we try to scan an invoice using IDR, In some of the invoices the identifying PO won't come and also that field will be non-editable too.
PO is approved and in open status, the buyer is also active

Content (please ensure you mask any confidential information):

Invoice is 2-way Order
and the System have only 1 BU with 1 ledger

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Code Snippet (add any code snippets that support your topic, if applicable):