After upgrading to 4.15 can´t upload new apk to published app in google play due to different certificate sign

i´ve been having troubles uploading heavy app to google play, first, in 4.14 version i did succesfully publish it, but for some reason i got the “unfortunately app has stopped” error, i guess there was a bug with the .obb file, because when i package the obb inside the apk file, everything runs just fine.
So i thought maybe that bug would be fixed in 4.15 version, so i packed the app again, but when i try to re upload the apk file (with the new version number) i got the error shown in the picture, telling me that i´m uploading an apk with a differente certificate, but that is not true, i´m using the same keystore file, and the same key information, since this version is a clone of the 4.14 version, so i don´t know what im doing wrong.
I really need help with this, thankyou very much.