Is the app update a simple download for my users ?
Only if it was signed by the same production signing key as you used originally, which would not appear to be the case here.
I didnt format my computer or changed anything about my eclipse folder or my folder where I save my keystore etc.
Despite that, you attempted to update an APK with one signed by a different signing key (e.g., debug vs. production). Use jarsigner -verify -verbose -certs ...
, where ...
is the path to your APK, to dump signing information, so you can compare your old APK to your new one.