Google Play APK Signing error.

Hi guys,
I have uploaded an app on Google Play around e months ago. When I wanted to update that app, Google Play told me that your app is signed in debug mode. So, I signed the app by creating a new keystore. Now, Google play told me that the app is signed by a different certificate.

So, I can’t update that app. Please help me guys, it’s really important.

To sign this updated version of your app, you need to use the same keystore that was used to sign the original apk that you have uploaded to Google Play. If you do not have that keystore then you would have to sign it with new keystore and upload it as a new app on the Google Play.