Interface could not be determined for basic type &1 and message type &2

What causes this issue?

An interface in the SAP Application Interface Framework could not be
determined for this message.
For the basic type/message type combination, no interface has been
assigned.

System Response

In a scenario where the IDoc is to be processed in AIF, the system sets
the message to an error status (Application Error). Because the IDoc
message could not be processed.
In a scenario where the IDoc processing is only to be monitored in AIF,
there is just this error message written to the application log for your
information. Because the IDoc message might not be in the monitoring
scope by intention.

How to fix this error?

Check if a valid basic type/message type combination is set. If not,
change the settings in Customizing for <LS>SAP Application Interface
Framework</> under <LS>Interface Development</> -> <LS>Additional
Interface Properties</> -> <DS:SIMG./AIF/INF_IDOC>Assign IDoc Types</>
and restart the message if in an error status.
Check which fields should determine the interface. You may then do one
of the following:
Change the settings in Customizing for <LS>SAP Application Interface
Framework</> under <LS>System Configuration</> -> <LS>Interface
Determination</> -> <DS:SIMG./AIF/INFDETI>Define Interface Determination
for IDoc Interfaces</> and restart the message if in an error status.
Cancel the message and send it again from the sending system (if the
data is wrong)

Procedure for System Administrators

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

Error message extract from SAP system. Copyright SAP SE.