You can "see" the switch on the app, AND you can get past the connecting screen, HOWEVER you cannot operate the switch. There are two possible fixes shown below. Please DO BOTH.
A> If the blue LED on the switch is SOLID, then another app on your phone has commandeered the bluetooth radio. Do the "refresh" sequence. SOLUTION HERE: https://bit.ly/2HaxGWf
B> If the blue LED on the switch is blinking in sets of TWO, then you inadvertently "factory reset" your switch, and forcibly disconnected it from the app. Please IGNORE the disconnected "image" of the device on the app. Re-ADD the switch to your app by pushing the big + button in the upper right. Then re-program the switch. SOLUTION HERE: https://bit.ly/2SuCTgR