Ok folks.. long story short, I was developing on a computer that I no longer have access to. I was able to retrieve the source code, but not the .keystore file used to sign
Now it is possible don't worry, here is the full and final steps to reset .JKS file.
Step-1
Download the UPLOAD CERTIFICATE (file name - upload_cert.der) from your Google Play Store Console
Step-2
Go to this LINK https://support.google.com/googleplay/android-developer/contact/otherbugs And fill the application form with your valid Email ID and upload the file (upload_cert.der).
Step-3
Now you will get the Email from support team, and they don't need your .JKS file but .PEM file here is the email Sample.
Step-4
to convert .JKS file to .PEM file you just have to download KeyStore Explorer
After replying the Mail, wait for 48 to 72 hours your keystore fill will reset.