Which is correct?

According to mobile app, my Ring Doorbell 3 is hardwired but the battery is down to 30%.
According to the webpage, my Ring Doorbell 3 is running on battery and is down to 37%.

I’ve gone through the process of resetting the device and running the setup again (and also checking that there’s voltage appearing at the end of the power supply cable) but it makes no difference.

This glorified doorbell is becoming more trouble than it’s worth.

Maybe both. The Ring App doesn’t display the battery % realtime. I don’t know about the web site.
Maybe the question should be, is the battery lasting long enough for your particular setup regardless of what the app/web is showing? If it is, then don’t worry about what the web/app has to say and just use the doorbell.
If it isn’t then tweak your setup for motion frequency and/or sensitivity to get the battery life you want.

Hi @icastle. To get an accurate reading of your Doorbells battery level, you can press the Doorbell button to trigger a recording. Give it a few minutes for the recording to stop and upload to the cloud. After this, your Doorbell will reflect an accurate battery level in the Device Health Menu of the Ring app.