Thanks for reaching out to us.
Error Code 2 suggests a network error and this is seen when ad request was unsuccessful due to network connectivity. That said, have you tested your Ad unit IDs with our
sample apps after getting the feedback? What is the error code that you are seeing in case of Ad request failure? As you are seeing the requests going through and as you are able to load test ads, this is not an issue with the implementation. If the frequency of the errors is very high, you contact our
AdMob Product Support Team as they will be able to assist you with Ad serving issues. You can also reach out to them through
this troubleshooter.