No entry found means it failed to identify device with querystring info you provided. Even if product type is wrong it gives this error.

That endpoint give same error code for device not found but message is "No entry found for device" instead of "No registered escrow key found" When my producttype value in querystring was wrong I was getting this error.

That endpoint gives same error code when device is not found but message is "No entry found for device xxxx:xxxx:xxxx" instead of "No registered escrow key found". You would get below response if you provide wrong producttype in querystring