ESP32-CAM-MB not working with my ESP32-CAM

Hi, I have an ESP32-CAM on which I started the project GitHub - jomjol/AI-on-the-edge-device: Easy to use device for connecting "old" measuring units (water, power, gas, ...) to the digital world. I connect ESP32-CAM using USB TTL UART and USB, which is powered by a 5V transformer. Everything works as it should, ESP32 reads the data from the water meter and sends it via mqtt to the home assistant. But I wanted to replace the USB TTL UART with something smaller, so I chose ESP32-CAM-MB, which I connected to ESP32-CAM, but ESP32-CAM does not work, the red light on ESP is on/flashing, but I cannot see the IP address of ESP-32-CAM .

Pointers to the devices actually used please.

Where are you expecting to see the address?
If the ESP led is on, it means it has power, so unless you also changed the firmware, it’s still the same as before, and the -MB is just used to power the ESP