I added a new OID mapping but it did not seem to take effect right away.
OID to Type mapping is cached in Asset Processor. There is a 10 minute cache refresh cycle. Please note this does not necessarily apply to caching of business rules as they impact the Asset Processor.
There is a configuration in web.config for the AssetProcessor "CacheTimerIntervalInSeconds" that sets a timer which when it goes off will refresh the cache. Alternatively stopping and restarting the IIS App Pool for the Asset Processor should also pull in new cache for the OID mapping.
Support does not recommend these workarounds as normal practice. Best practice is to set the OID mapping and know that it will take effect only on messages that begin processing at least 10 minutes later.