If you use the ESP32Cam with the shield which is the easiest to use you may find the shield blocks the built-in WiFi antenna on the ESP32Cam if it's pointed away from the router.

I had this issue where it works fine where I programmed it but mounted where I wanted it would send the email with no attachment.

If you can't get it to work by raising or lowering or tilting it you can try removing the shield and powering the Cam separately or adding a WiFi antenna. This requires moving a teeny, tiny resistor. I tried that before and trashed the cam board. Good luck.

https://randomnerdtutorials.com/esp32-cam-connect-external-antenna/