Hi Steve,
I’m not sure. It could have to do with the fact that you are doing this with a Reactive Web Application as those are based on a different technology compared to Traditional Web Applications where this Platform Extensibility API was originally designed for.
You could of course test the functionality within a Traditional Web Application first to see if it works over there.
Furthermore, did you make sure you have met the mentioned conditions from the API documentation?
- If there is a single query that uses the Database Connection with the old database before this action is executed, the switch to the new database will not happen until the end of the current request. Only in a next request the database switch becomes effective.
- The Connection String must connect to a database with the same type (e.g. Oracle, SQL Server, MySQL) as the one configured in Service Center for the Database Connection.
- Your license must include the Platform Extensibility APIs feature.
The first condition is an important one, as you need to make sure no query is executed using the default database connection (DB1) within a certain request, before you make the switch to the DB2 connection. Otherwise the switch would become effective only from the next request onwards.
The second condition I’m sure is met right?
For the third condition, login to Service Center >> Administration >> Licensing and look for ‘Platform Extensibilty API’ to check if its included in your license (for Personal Environments it is included).

Hope this helps.
Regards,
Nordin