UART2 doesn't receive data

[ypain1970]

I'm about to marry esp32-wroom and SIM800L modem. ESP32 works fine - no problems with flashing or accessing i2c LCD screen, but UART2 just sends data but never receives anything.

I've connected other terminal using USB2COM converter instead of modem, it confirms that data is sent correctly, but still no luck getting anything back.

I'm accessing UART2 using GPIO pin 16 and 18 on the breadboard. I've tried both Arduino IDE example code and esp-idf example code with the same results.

What could be the reason?
How to debug it further?

Is it possible that RX signal generated by modem or usb2com has too high voltage (5v instead of 3.3v) and how to check it?