Same problem. I log in, sit at the loading screen for about 15 minutes, then get booted. I just came back this month and I'm starting to wonder if maybe that was a mistake. It seems the forums are filled with people screaming into the wind that they can't log on or play, and all I see is that apparently standard maintenance is complete. No help anywhere for anyone...
If you are away from the game for a certain amount of time, the server will disconnect you automatically.
This may also happen during particularly long loading times when the server is busy or if you haven't touched your controller in a while.
The Elder Scrolls Online: Tamriel Unlimited - ZeniMax Online Studios
Also having the same issue, have been pressing "enter" at random and clicking the load screen to "remain active." Going on an hour this morning and was still at the load screen.