I had the development team review the Nest integration and things seem to be working properly. I tried one as well and it seemed to connect fine.
When you click Accept on Nest you should be redirected back to our site, and it can take 5-10 seconds for the Nest Home to show up in the integrations panel.
What browser are you using? Maybe try a different browser to start.
I'll ask our web app team if they have any troubleshooting we can try.