Android apps are signed with a private key. To ensure that app updates are trustworthy, every private key has an associated public certificate that devices and services use to verify that the app update is from the same source.
NOTE: ONLY THE ACCOUNT OWNER CAN DO THIS
Step 1 - Go to Play Console
Step 2 - Select the app
Step 3 - Under "Release", select "Setup" and Click on "App signing"
Step 4 - Scroll down to Request upload key reset section
Step 5 - Click on Request upload key reset
Step 6 - This will ask for .pem file which is to be provided by Appbrew team
Step 7 - Upload the file
Play store take around 3-4 days to reset the keys