I have tried both the Galaxy watch 4 and a friends Galaxy Watch 5 sensors on my wrists. The heartbeat sensor in which it uses to detect if you are wearing the watch cannot pernitrate dark ink. It is a very simple fix to add option to turn off the wrist detection or "Do not disturb while off wrist" type setting but samsung will not do it, and hasn't listened to its customers since the Watch 4 came out, so do not hope for an update with this feature. If your pigment in your arm is dark enough, not even the stickers will help.
People say that it is Google and WearOS's problem, but is not. Fossil smart watches run on Wear OS, and have this feature and work fine.
Do yourself a favor and refund the watch and get one from a company who cares about its customers.
