Loads of threads on this, none of them address the simple fact that this should be easy...yet its not.
My 810 paired on other phone (s9) device which I have cleared and wiped. The new phone pairs once, then says disconnected they only way to even get that far is to delete all phones and connections and start again.
To me this is clearly an issue with android and Samsung gui and garmin, so please sort it out Bluetooth pairing is simple stuff