Cannot import file; Customizing entries for interface &1 missing

What causes this issue?

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

System Response

The system does not import the file.

How to fix this error?

In the Customizing activity <LS>Specify Incoming Templates</>, check the
setting for the interface while maintaining the incoming template types.
Ensure that entries are made for the following fields:
<LS>Document Type</>
<LS>Application</>
<LS>Product Safety Document Type</>

Error message extract from SAP system. Copyright SAP SE.