A person is the integration
Two systems that do not talk, and between them somebody who copies numbers from one screen to the other. That person is a single point of failure with a holiday.
"That is not supported"
The courier, the bank or the marketplace you actually work with has no ready connector, so the answer becomes: change the courier.
The standard does not do it
One step in your process is yours alone - and the system says no. So the step moves back into a spreadsheet, out of sight of every report.
The data is locked in
Getting figures out means an export to Excel, and getting them back in means somebody retyping. Nothing is wrong, and nothing is connected either.