My best guess would be your router is blocking some type of traffic.
Here is what I would do.
Unplug your internet modem.
Unplug your router.
Unplug your SmartThings hub.
Reboot your phone.
Once your phone is back up, plug in your modem.
Once your modem is online, plug in your router.
Once your router is online, plug in your SmartThings hub.
If your problem continues check your routers firewall and/or setup a static ip for your hub and add rules for ports 37, 39500, 1111, 9443 to route to your ST hub. The static ip and port forwarding should not be needed but worth a try.