Unfortunately, this issue seems specific to your company's set-up. Users on this forum do not have access to your set-up. I recommend reaching out to your Concur Administrator. If you do not know who that is, it may be listed on the Concur Home Page under the "Company Notes" section. Or, reaching out to your supervisor, Finance or IT and they should be able to direct you to the correct person.
Did you tried updating COMMENTS section with whatever exact receipt number and upload the receipts, Incase receipt number field is mandatory, update it as RECEIPT1 and inform your approver in the COMMENTS box. Lets try.