BLYNK_V1.4 20-8-11 with SIM800L, help with pins to SIM module please

[amiiit]

Hello,

I have got a board with the above labels, but with a SIM800L. I can't find this documented anywhere:

I have tried all the examples and specifically with the following pinout:

tx: 26
rx: 27
power: 23
power_key: 4

It seems like the power is correct, as I see blue lights blinking when I set 4 to HIGH. I am able to send stuff over the UART1 with 26/27 for TX/RX but I don't receive anything. I tried with both 115200 and 9600 baudrates, as well as flipping the RX/TX values, but with no success. Could you please confirm what is the correct gpios that are connected to the SIM module?

Thank you