Removing your Google Activation Lock Online
An activation lock is a security feature that prevents others from accessing your phone if it is lost or stolen. Before returning, replacing, or selling your phone, it is important to disable the activation lock. If you don't remove the activation lock, no one else can use the phone.
Instructions
Log into your Google account. Go to Device activity & notifications under Sign-in & security.
Next click on Review devices under recently used devices.
Choose the phone you want to remove from your Google account and click the red Remove button next to account access.
A confirmation window will appear. Click Remove.
A message will appear saying that access has been removed from your device.
To check, look at the list of recent phones. The chosen phone will say Access removed.
After removing the Google account access online, go to the phone's settings to reset it. On some phones, you might need to enter the Google account info during setup after a hardware reset.