SIM800L EVB + Arduino UNO + StepDown LM2596

I have buied a SIM800L EVB module and i can't make it working. My first step has been simply connect the 5V pin on the module with arduino 5V pin
gnd with gnd
tx to 8th pin
rx to 9th pin

and the module keept restarting; after a quick googling, i have purchreased a LM2596 DC-DC Stepdown and rewired the thing as showed in the pic.

The converter is set to output exaclty 5V at ~2.2A, i have strippet a 12V powersupply and connected as the picture shows, one in the jack and one in the dc converter.

When wired directly, even if the module keep restarting, i have got some response from the AT command, after this wiring no response over the module (probably fried?) so i have purchrased another one and done the same error that i can't decifre

The led on the moduke keep blinking and even show that it has connected to the network

I'm really getting mad, i have buyed 5 modules tried different wiring, and i can't undearstand what i'm getting wrong, so please help me, any advice will be welcome.

Maybe i am not using common ground?

Here is some base code i'm using to test it

#include <SoftwareSerial.h>

//Create software serial object to communicate with SIM800L
SoftwareSerial mySerial(8, 9); //SIM800L Tx & Rx is connected to Arduino #8 & #9

void setup()
{
  //Begin serial communication with Arduino and Arduino IDE (Serial Monitor)
  Serial.begin(9600);
  
  //Begin serial communication with Arduino and SIM800L
  mySerial.begin(9600);

  Serial.println("Initializing...");
  delay(1000);
  
  

  mySerial.println("AT"); //Once the handshake test is successful, it will back to OK
  updateSerial();
  mySerial.println("AT+CSQ"); //Signal quality test, value range is 0-31 , 31 is the best
  updateSerial();
  mySerial.println("AT+CCID"); //Read SIM information to confirm whether the SIM is plugged
  updateSerial();
  mySerial.println("AT+CREG?"); //Check whether it has registered in the network
  updateSerial();

  
}

void loop()
{
  updateSerial();
}

void updateSerial()
{
  delay(500);
  while (Serial.available()) 
  {
    mySerial.write(Serial.read());//Forward what Serial received to Software Serial Port
  }
  while(mySerial.available()) 
  {
    Serial.write(mySerial.read());//Forward what Software Serial received to Serial Port
  }
}

SOLVED:

The module was actually fried.

It turn up that you can actually run the sim800L module with only the arduino UNO if you solder a capacitor EEUFR0J182B like the picture

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