Glad to hear you got it working!
It sounds like you probably already know all of the following, but just in case, here is the FAQ on setting up your network. Read post 11 first, then go back and read the full thread.
One more thought. While I understand the marketing reasons for the decision, the fact that SmartThings gives customers zero guidance on how to set up a network backbone does lead to a lot of frustration that shouldn’t have to exist. if people knew that
.1) The hub should be located centrally in the home, both vertically and horizontally. Don’t put it in a garage or basement as those have concrete and pipes and metal objects which will reduce signal. If your Internet router is off in some inaccessible corner, you can use a Wi-Fi access point that has a ethernet port on the side and plug into that. Also, the hub should not be put in a cabinet. You just want to make it as easy as possible for signal to spread around your house.
.2) you need one device that can repeat about every 40 feet…