What I was telling is that I was happily compiling any of my programs, either in debug or in release mode. No problem. For that reason, I completely forgot keystore issues. Then I became to develop the Firebase App. I met a problem, that I don't submit here because it is almost incredible and I prefer to try to discover by myself. Trying to make a simple App reproducing that problem, suddenly, appeared this error. Believe or not, I didn't create that Fireapp.keystore .. Of course this sounds incredible and better to stop this discussion, because I have no proofs of what I say. I repeat that I didn't create any Fireapp.keystore. Perhaps inside some tutorial that I used as a base skeleton? I hope that this has been my problem only. Of course I recreated a new keystore and overcame the problem. Thanks again.