Make sure that under OPTIONS, GENERAL that you have the box checked to START TEAMVIWER WITH WINDOWS
Normally the TV session would logged off when you manually select exit TeamViewer option. If you are using SSO Login you should not face any problem otherwise while signing in please enable the checkbox "Keep me signed in" and give it a try.
If it is not helpful share your exact usecase which you want to acheive connecting TV after reboot.
The host computer is online with teamviewer running. When I try to connect, it flashes (as though it was trying to open the pop-up window) and then nothing happens. Any help?