UPDATE: I was finally able to provision the thermostat and connect it to my home network. Once the thermostat was connected to my network I was able to setup the thermostat on my Pi Gateway with no problem at all and everything is working perfectly now.
It was no easy task to get the thermostat connected to my network. I tried to provision the thermostat with Windows 10, Android, and Linux. None of these OSes were able to connect to the thermostat. I even spent 2 or 3 hours with a software engineer friend of mine, trying to get Raspberry Pi Stretch to connect with no success. The only way I was able to connect was to connect using Apple OS. I'm not sure why all those other OSes wouldn't connect, but my best guess is that the wifi module in the thermostat uses the very old and very unsecure open WEP protocol with no password and the only OS that supports open WEP with no password is Apple OS. I tried this on a very old iPad and on a modern up to date iPhone and both connected with no problem.
It doesn't make sense to me as to why, at least, Linux doesn't support open WEP with no password and why only Apple OS worked. But I just wanted to let everybody know that if you purchase a CT50 thermostat with the idea to connect it to the Pi Gateway you will need to provision it using an iPhone or iPad.