@phitou 

Hi, I think you need to ensure the motion detection feature is working on the Tapo camera first. If so, you can disconnect the Tapo C200 from the NVR and then reconnect for a try.
I found another thread Motion Sensor missing in HA integration, and think it may help you.
 

  @Summer_S notifications on the tapo app also are completely broken, not only for C200 but also for C210.
Until I restart the camera, there is no notification on the tapo app , so it's even worse than what i thought.
After restarting the camera, it only works for a certain amount of time ...

  @phitou 

Hi, you can go to the Tapo app-->camera settings-->detection&alerts page to check if your motion detection/AI detection and Activity Notification features are enabled and check if this link is helpful.
On the top right corner of the Tapo app, if the notifications of the camera are displayed in the Message icon, the notification feature of the Tapo camera should be ok.
 

  @Summer_S of course it's enabled, as a restart of the camera make the notification (inside tapo app) work again, for a certain amount of time ...

Restarting does not fix onvif events however

  @phitou  you can try to disconnect the camera from the NVR and then reconnect to check if the onvif events will work again. 
If your case is similar to this thread, you can also upgrade the tapo integration in the home assistant for a try.

  @Summer_S removing and recreating the camera on the nvr didn't fixed it.
Notifications are also broken in the built in tapo android app.

When i enable the alarm on the camera itself, I hear it when i'm moving in front of the cameras, so the camera detect it, but it's not transfering to tapo app or the nvr (via onvif)