Check the process_code in the po_headers_interface and po_lines_interface, if it is ‘REJECTED’,

select process_code from po_headers_interface;
select process_code from po_lines_interface;

please do the following:
Run the program – Purchasing Interface Errors Report
choose parameter : PO_DOCS_OPEN_INTERFACE

The report will list all the errors you have during importing. You can fix the data, then reset process_code = Null in both interface tables, rerun the Purchasing Document Open Interface.

update po_headers_interface set process_code = null
where process_code = ‘REJECTED’;
update po_lines_interface set process_code = null
where process_code = ‘REJECTED’;