@hokpe I'm having exactly the same problem.. I bumbed up the sensitivity and still nothing. I also thought it could work in pair with the Tapo T100 motion senso, but they haven't introduced this feature yet. Im using the 1.3.10 firmware. 

  @hokpe well although my 2 C425 work better, the issues are still not resolved. although you fix a trigger range area, the cam might still trigger movement far outside the area.

also 1 constantly gets firmware updates and the other only far far later if at all... 

sensitivity is an issue, person detection and movement is an issue... sometimes (the 2 are concerned) frame the movements person pet whatsoever, sometimes not...

all in all the software / firmware is not very good.

  @hokpe My C425 functioned perfectly upon setup several weeks ago. And then I complained to Support that the unit suddenly stopped detecting motion UNLESS YOU WERE VERY CLOSE TO THE UNIT. I also noted that the TAPO software had been updated November 8, 2024.

Tapo Software and Firmware were already up to date but Tech Support answer was to update the firmware and software!! 
 

I may have found a better solution: Delete both the Cache and the Data for the TAPO app, from within the phone settings for Apps (not within the TAPO software itself), then delete the TAPO app and reinstall it, then login, and your camera(s) should reappear with no issue. That seemed to correct the detection problem though I can't be 100% positive.

  @Walt_2024 I would assume the camera should detect and store motion independent from the app on your phone. In my case it also suddenly stopped detecting. Green led does not light up and there is nothing on the SD card. Live view is ok and motion is clearly detected when viewing live (blue rectangles). It just does not act on it. Second cam with the exact same firmware works fine. Switched the two cams and the problem moves with the camera. I will still try your proposal, just in case :-)