Treated myself to an upgrade from my perfectly functional Galaxy watch to the new watch 4 classic. As you may probably guess from the title it doesn't vibrate because of the tattoos I have on my left arm. Turned my watch over, works. Put it on my right arm, works. This didn't happen with the old watch, it's the feature where it will not vibrate if the watch doesn't think you are wearing it and you can't turn this feature off! This is really shocking, you would think a watch as expensive as it is and made by a company such as Samsung wouldn't have this type of issue. Completely unacceptable
If you have seen that post about the 10mm x 1.5mm clear silicone dot and read the comments then I can absolutely 💯 agree that since I've used that technique, my galaxy watch4 classic has been working perfectly 👌
Like yourself, I have a heavily tattooed arm and had all sorts of issues with the sensors, mainly the watch locking itself constantly because it couldn't detect if I was wearing it. As I like to samsung pay then this was quite frustrating having to put my pin in everytime it locked!
Now I don't have that issue and even the other sensors work now for example the blood pressure, ECG compression sensors 👍