The LAN device IP is not accessible when a SSH session is not running

Hi there I have a python script which reads data from different IP addresses in LAN, The script runs in a Edge Device with Ubuntu 20.04 LTS focal installed every 5 min using a CRON job. The problem is very weird, when I SSH into the device, the script simply works but when i close the SSH session, The cron starts the scripts but IP addresses does not respond or not pingable.

What I tried is following but none of the approach worked for me.

1. Converted code to service
2. Disabled device sleep/suspend
3. Enabled networking service
4. Tried to enable autologin assuming it let the session opened

Looking forward for a solution of this problem, The python script which is executed by the CRON job is following

import subprocess

def ping_ip(ip_address):
    try:
        result = subprocess.run(['ping', '-c', '1', ip_address], stdout=subprocess.PIPE, stderr=subprocess.PIPE, text=True, timeout=5)
        if result.returncode == 0:
            return True, result.stdout
        else:
            return False, result.stderr
    except subprocess.TimeoutExpired:
        return False, "Timed out"

def main():
    ip_addresses = ["192.168.1.1", "192.168.1.2", "192.168.1.3", "192.168.1.249"]

    for ip in ip_addresses:
        is_responding, response = ping_ip(ip)
        if is_responding:
            print(f"{ip}\tResponding")
        else:
            print(f"{ip}\t Not Responding")

if __name__ == "__main__":
    main()

The CRON job itself that runs this script every 5 min is following

*/5 * * * * /usr/bin/python3 /home/nvidia/our-script/pinger.py > /home/nvidia/our-script/lastrun.txt

I just discovered same script is working flawlessly without any user login required on device boot on Ubuntu 18.04