@detailme: The latest Nest plugin works only with UI7, so I'm afraid this is the likely reason. Also you'll need the latest firmware as we made some changes to to assist the plugin in fixing some of the bad stuff we had.
@roelofzo: All versions are available, you just need to know the URL to it. See previous posts for 0.48 if this is what you really want to do, however, there are a lot of fixes in 0.68 (like auth/deauth issues that were present before).
@tbully: It's inconvenient but we aim for this to be temporary. We're not resting on our hands. We had some similar road blocks with Alexa and we got past them. Imagine a burglar shouting loud through the window: Alexa open garage door. If we solved this we're going to get past these problems as well. Some small news here, we're reworking the way our thermostat UI looks on mobile and web, hint: 1/2 set points anyone?