If you have the original proof of purchase (receipt), you can submit an official support request to Apple to have the lock removed. Apple Support Activation Lock for iPhone and iPad - Apple Support (CA)
However, modern iOS versions like 15.5 are highly secure. Unlocking a device requires a digital handshake with Apple's activation servers . A simple file download on your computer cannot change the status of a device on Apple's end. Legitimate vs. Fraudulent Methods icloud unlock all iphone ios 15.5 plist file download
If the device is yours and you simply forgot your credentials, use the Apple iForgot portal to recover your account. If you have the original proof of purchase