Please uninstall your Android app from the device and run the app again.
Now you will get a new registration Id. That may solve your MismatchSenderId problem in a specific case (Sometimes it happens If you change/refresh your API key, but still using the old registration key). In my case, I got the registration Id first for my device and then I changed my API Key (on Google GCM server) and then I got MismatchSenderId error. Finally, I uninstalled my Android app from the device and the problem got solved.
