Capture GRAYSCALE image with ESP32 Cam
I just tried this with my ESP32Cam with no problems.  I would check that you are supplying enough power; I've definitely seen the 'Camera capture failed' when I had power issues.  Also, I would try a more recent tutorial on the ESP32Cam; the latest Expressif ESP32 Arduino libraries have AI Thinker ESP32Cam as a device choice.  I would try the CameraWebServer example in the ESP32 library and see if you still have the problem.