Why SAP Integration Suite, managed gateway for spend management and SAP Business Network maintained parameters or cross reference values are not working?

Please verify possible solutions:

1. Check the SystemID coming up in the before mapping file and make sure a connection exist for the same. If before mapping file is from Ariba Procurement then make sure realmid showing up in the payload is associated with at least one Managed Gateway for Spend&Network connection.
2. The connection should be marked with respective environment where the transaction should be working for e.g. Test or Prod or Test/Prod.
3. This connection should be part of Managed Gateway for Spend&Network project for respective product and status of the project decide the working in respective environment i.e. the Managed Gateway for Spend&Network project which is in In Testing works for test accounts or test realms only whereas In Production works for prod and test provided the connections are separate for test and prod.
4. In case of Custom Routing the connection or SystemID which is getting replaced should be as above.
5. Example Scenario: If a connection is marked with test environment alone and you are seeing the issue in prod transaction, then at least one connection with that SystemID should be marked with Prod environment and it should also be part of a Managed Gateway for Spend&Network project which is in In Production status.

Please make sure the steps of FAQ Why Managed Gateway for Spend&Network project changes are not applied to the documents? are done.

SAP Integration Suite Managed Gateway > Managed Gateway for Business Network
SAP Integration Suite Managed Gateway > Managed Gateway for Business Network SCC > Managed Gateway for Buyer Business Network SCC
SAP Integration Suite Managed Gateway > Managed Gateway Foundation & Tools > Managed Gateway for Managed Gateway Portal