Connect to Decathlon Dual HR

Hi,

I recently bought Decathlon Dual HR chest strap heart rate monitor. On Day 1 it connected to Apple watch like a charm. But, since then it is not connecting to the watch. Please find below the things I have tried:

1. Unpaired the device using Forget device and tried reconnecting
2. Tried waiting for 2-3 mins for the devices to connect
3. Connect the Heart rate monitor with my iPhone - It works without any issue.

Can anyone please help me figure out why I am unable to connect the heart rate monitor to the watch?