If you are unable to see any logs in tracer, it means that you did not run or you run different service or activity. Can you try to trace different service? Please also check logs for environment in System-->Operations--Logs for any errors there just to confirm that all works correctly.
In case if you are using SoapUI or third party tool to test it, it could be that the request is not reaching a pega server and the service never initialized, so you could not see the logs in the trace.
Could you elaborate more how you are trying, which is the service, etc