I have been reading about this topic and seems like be it on Apple watch or Samsung watch, the same issue occurs. The issues about the waiting of the SMS about successful subscribe to the number share VAS or the pop up error message about the watch or plan being not compatible with Numbershare. So what has starhub done about this?
For my case, I was able to subscribe to it on my Galaxy Watch 4 LTE, and after a while, I realise that I am not getting the LTE service when I'm out for a run, further check on the watch and wearable app revealed that the service has been turn off. So the only way to solve this is to remove all plan since I no longer able to toggle the on and off either on the watch side or the wearable app. And there you go, once you try to set it up, the error message will pop up saying that your plan is not compatible with numbershare. I have to call starhub and make sure they do a reset and probably wait for 1 to 2 days before I can reactivate the plan again. And this happen for 4th times now while I write this and I'm still waiting from starhub reset to take effect before I can reactivate it and subscribe again. Looks like I'm not alone, so what is starhub doing? So many engineers and no one has a solution?