Means-of-transport category for stage &1 cannot be determined

What causes this issue?

No mode-of-transport category is entered for means of transport &V2& of
leg stage &V1&.

System Response

Since the route information is incomplete, the system cannot process the
request &V3&.

How to fix this error?

Check the master data Customizing for means of transport in the table
/SAPAPO/TRTYPE.

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.