Trip schema &1 in morei &2 does not exist in table T706S

What causes this issue?

You want to edit a trip that was created with a trip schema that no
longer exists.

System Response

The system does not allow you to process such trips.

How to fix this error?

Please enter the missing trip schema in table T706S.

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.