How to block factory reset on a lost device?

Hey, Thanks for reaching out to us.

To prevent anyone from using your phone once it is lost, you can enable the ‘lost mode’ on the stolen device. The device will be locked down with the phone number to contact the owner, a message from the owner and footnote displayed on the screen of the device screen.
To instantaneously enable the lost mode on a device, navigate to the Manage tab and select the desired device. Click on the Actions button and choose the ‘Enable Lost Mode’ option. Enter the phone number, message, footnote and click on Continue.
The lost mode can also be automatically enabled on a device after it has been inactive for a certain time period. Navigate to Admin-> General Settings-> Android Lost Mode Settings to set the number of days the device has to remain inactive for the lost mode to be enabled on it.
Need more info on this? Have a look at enabling lost mode on Android devices.

You can also enforce the Factory Reset Protection on the Android devices such that the device will remain unusable until you log in using the Google account that was already set on the device before factory resetting it. Navigate to Policies-> Android-> Advanced Restrictions-> Factory Reset Protection (Google Account Verification) to configure the same.

Wanna know more? Check out Factory Reset Protection on Android devices.

Cheers!
Grace Baker
Hexnode MDM