Always double-check that you're logged in. Maybe it's an issue just with my phone, but it seems like the site wants to forget me on it. I've almost missed out on Game Vaults because of it.

You have to set “remember this device“ in your account settings, after you've logged in with your mail.

You have to keep a page from the site open and active on your device, which is difficult because tabs sleep if you switch from them or if your device turns the screen off. Honestly it's more trouble than it's worth on mobile..