@Rahool_Tariq , Okay, that’s the problem, probably the update deleted the IMEI. Now there is only one of two solutions, you have some old phone that does not use so you can use the IMEI of that phone?
@Sergio_Guerreiro , from what I can make, only make with MTK devices, but I’ve seen somewhere who has done it on other hardware. It is a matter of searching. Google is our friend.
We can’t have illegal tools posted on this forum. These tools are illegal in most countries - that’s why the tool is not linked. If it is it will be removed.
You can use the MTK engineering mode shortcut from the play store to get to the menu and you need the sim card in the watch.
I am surprised you have not found what you need on the Web. It takes a couple of minutes to find it.
Anyway - do not post links to any IMEI changers please. Thanks