@Babavoss 

Hi,
You can refer to the link below to check if the configuration steps are correct.
How can I view my Tapo camera on PC through the RTSP stream?
 

Please help confirm the following information for further analysis.
1. Please check the firmware version of the camera and the Tapo app version, to ensure they are up to date.
2. What URL are you using to set up the RTSP stream? 
3. What error message do you see when you fail to set up the RTSP stream, and which step do you stuck on?
4. How many devices stream the camera simultaneously, via the Tapo app or RTSP/ONVIF stream?
5. You can check if you can add the camera successfully via the iSpy or VLC program on a PC.

Best Regards