Hello. I spoke to Samsung Tech support. This is a global issue for all Samsung Gear devices. The new iOS 11 revisions to Gear Fit and Gear S apps has difficulties establishing a connection to the watch and maintaining it. That means that even if you manage to connect your watch to the iPhone, it will eventually disconnect and never reconnect again until you reset the watch and make a new connection.
when I asked Samsung about when this issue will be fixed they said it will likely not be fixed until 2018 because the issue is with the app and the watch. Unlike other bluetooth devices that naturally talk to each other directly (no app needed), Samsung Gear devices cannot synchronize to the phone without the app. iOS 11 does not support background Bluetooth signalling like it did in iOS 10 or earlier. Samsung has stated that only iOS 9 is best for Samsung gear devices and only works on iPhone. Their compatibility tests are for old devices and they have no coverage for 2017+ iPhones.
i am very frustrated with Samsung and I’m going to make sure they give me my money back after making me spend money for a falsely advertised product.
