I'm testing an ESP32-CAM that I recently bought and haven't used before. To test it, I am using Arduino IDE and the CameraWebServer example, I put the password and name of my Wi-Fi, also I changed to the camera that I think is the correct one (#define CAMERA_MODEL_AI_THINKER).
When I disconnect GPIP0 from GND I receive the following message:
According to the error message, the program was not able to find the camera. If you installed the camera yourself, as some ESP32-CAM kits require, then the flat camera cable is probably not seated correctly in the connector.
Disconnect and reconnect the camera cable, and try again (several times, if necessary). It took me a few tries to get it right, following an on line video that showed the process very clearly.