I just wanted to post this thread as I have just had a Nest Learning Thermostat installed alongside my new combi boiler here in the UK.
When it came to the boiler installation engineer setting up the Nest Learning Thermostat they could not get the thermostat to connect to my wifi despite numerous attempts by both the engineer and myself. He was perplexed as he had fitted many of these and never had any issue connecting the thermostat to w wifi when the correct wifi and password had been used.
Whilst the fitter continued finishing off the installation I continued to try to connect the thermostat and despite definitely selecting the correct wifi and entering the correct password on the thermostat it continued to fail to accept the password and connect. I had already done all the other things that the other forums and google help had suggested such as resetting the thermostat to factory, rebooting my router etc and none of them worked.
After several hours of looking on forums I finally stumbleded across the solution. Luckily for me someone had posted that they had recently set up two nest thermostats during which they had set up the first thermostat ver quickly as they did not have much time and decided to leave the second thermostat to the next day when they had more time. The first one had connected without any issue and the second thermostat the they were setting up the following day kept failing to accept the correct wifi password. They discovered that because they had a long password around 30 characters/digits/symbols in length that on the second thermostat when they were setting it up they were taking there time and checking the password more thoroughly than on the first occasion when they rushed the password. It turned out the there appears to be a set time for actually entering your password and if you take too long it will not correctly register. The solution is to be as fast as possible entering long passwords. I had been slowly entering mine and double checking all the time and this was too slow. When I entered the password as fast as possible it worked first time.
Anyway hopefully this will be useful for anyone else who is entering a long wifi password and struggling for the thermostat to connect to their wifi.
