Arduino Ethernet shield W5100

Hello,

Has anyone encountered an issue where an Ethernet shield does not work when an Arduino UNO R3 is powered by a 9 V adapter?

When the Arduino is connected to a PC via USB, the shield starts up immediately and everything works fine. However, when I disconnect the PC and power the Arduino with a 9 V / 1A adapter (I tried more of them.), the shield does not initialize. Only the PWR LED is on, and nothing else happens.

If I press the reset button on the shield, it starts working right away.

Could this be related to the fact that I am using a static IP address?

I am using VS code + Platformio.

Thank you in advance for any advice.

#include <SPI.h>

#include <Ethernet.h>

byte mac[] = {0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED};

IPAddress ip(192, 168, 143, 105);

IPAddress gateway(192, 168, 143, 1);

IPAddress subnet(255, 255, 255, 0);

IPAddress dns(192, 168, 143, 1);

void setup() {

delay(1000);

pinMode(4, OUTPUT);

digitalWrite(4, HIGH); // disable sd card

Serial.begin(9600);

Ethernet.begin(mac, ip, dns, gateway, subnet);

Serial.print("IP: ");

Serial.println(Ethernet.localIP());

}

void loop() {

}