It's the same here for me, I just opened it right now and it somehow logged me out even though it was set to logged in, and I currently can't login again. I assume that they are doing a maintenance check(?). Let's just to wait for it and hope it'll come back again. Browser mode still works, so it's still good.
Same 
Was logged out and the login button no longer works at all.
The site was out ~10 hours ago and the app stopped working since.
Same with me when I open it for the daily 100 SG from the appzone. They most likely did some changes to the server because there was some kind of checking when I open this site in my browser just now.
Same for me, I uninstalled and reinstalled it again and it fixed it though
in 3 steps
Choose the game that interests you and play itfor free.
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Is gamehag app not working? It keeps asking me to login and nothing happens after i enter email and password.
also continue as a guest is not working.