issue solved after following the below steps.
1. Reset the Heat Link E.
2. Press on the button that says Nest and hold it until the LED goes from green to blank (off) to pulsing blue to solid yellow. a. Once the light is solid yellow, release the button, and in a few seconds, the pairing light will slowly pulse. (This time, the light should stay on longer and not go out in 5 seconds.) b. Add the Heat Link E again. Once it's connected, the thermostat should continue the setup.
3. Enter the room name, schedule, and Eco temperature.
4. Test the thermostat.
5. Tap Finish.
I want to ensure you are good to go, and everything is working properly. Please let me know if you are still having trouble, as I will be locking the thread in 24 hours due to inactivity.