I have deployed a contract which was UUPS upgradable contract unfortunately I did not use the @ to define the version.
Proxy address and Implementation address is verified.
I wanted to add new functions so I copied the verified Implementation contract's code added new function and tried to deploy it. It is getting failed.
Also in failed transaction it is calling upgradeTo instead of upgradeToAndCall
Please provide more info: what are the addresses, how you are deploying the new implementation, how you are trying to upgrade the proxy, what exact errors you are getting.
Actually I figured it out. For some reason remix was calling upgradeTo instead of upgradeToAndCall causing upgradation to fail. I manually called upgradeToAndCall and it worked!