Hey Jerry. I had the same problem with my CT100. I bought mine on Amazon through one of their warehouse deals, so I got a great deal but it also means that it has been used before. Because of this, the previous owner synced the CT100 to their z-wave hub but never un-synced it, which made it impossible (regardless of doing a hard reset of the thermostat) to sync it to a new hub. I returned this used CT100 to Amazon and reordered a brand new unused one (never been synced before). It worked/synced to my ST hub almost immediately. I don’t know if your CT100 is refurbished or previously used, but that may be what is happening. I hope this helps! 