Did you read just (at least) the last 2-3 pages of this thread? Or maybe the 101 document linked in my signature? That would be my suggestion.
When you configured the DB1 with ezviz app, did you configure the chime? mechanical or electonic chime? the problem is that after the first config, the ezviz app doesn't let you change the chime options, they removed the option menu from the app. So, in your specific case, if you can't manage to use GV app, or Hikivision mobile app, which have the chime options menu always available, also after the first configuration of the doorbell, what you can do with EZVIZ mobile app is remove the camera from the app, and reconfigure it from scratch, like you just got out of the box now. So add the camera again from the app, and the wizard, once it sees the camera, will then also ask you if you have a chime connected, what type of chime and if you want to enable it.
You did install the power-kit of the DB1 right?
Yes, I read 101 (more than once) and had searched this thread for "chime" and spent the past 2 days searching Google for a solution before I posted here. I did not come across anything in my search that mentioned the chime working, then suddenly not working which was not related to the chime itself or the transformer. It wasn't until I saw your response that I got an indication that the problem I was having could be a software related one and not a hardware related one. I didn't realize there was a hidden chime option in the EZViz app that would disable at random until I saw your message.
I removed the device from the EZViz app and went through the setup again. Chime works again. Hopefully the chime will stay enabled more than a few days this time. Thank you for your response. That and your response to the other person got me on track to resolving this issue.