itch.io

If in the settings you see that you signed in as a guest, then to log in you have to close the game(or reload page if browser). Then start game again and you'll have a screen to sign in. 

If that's not helping - > close the game, clear cache, try to start. 

If still not working for you - > collect some screens, showing the problem, and go DM dev on Patreon with your account name. 

The game only asks you to sign in on startup. So restart it to get the dialog.

The sign in screen is skipped in 2 cases: you're already singed in OR game detected no internet connection. So (if you don't play in browser) your firewall or device settings might also be a problem.