@FlomaS 

What type of SD card are you using? Security cameras perform frequent read/write operations, and lower‑quality SD cards can quickly show instability or even fail under this kind of constant use. This article should help, take a look. What should I do if the SD card cannot be formatted/recognized?

Alternatively, you may consider changing another sd card. You can find a compatible model or type from the guidance here: microSD Card Compatibility for Tapo and Kasa Security Cameras

As for the viewing issue, please ensure your Tapo app is updated. Do not enable VPN on your phone while using the Tapo. Please check if you can watch the camera locally -- when your phone connects to the same WiFi as the camera. You may try to log in to the Tapo app on another phone and check whether the same thing still happens.