I made an account for Pokemon go and when i went to the loading screen today, it said it couldn't load and it gave me an option to sign out...so I did to see if I could reload the game and maybe it would let me on, but now every time I put my username and password in and I click the sign in button, it says "unable to authenticate. please try again" and I try and try but it never lets me in. PLEASE HELPPP!😁
I have the same problem, it may be hard to log in but its possible, In order to log in you have to keep signing in, non-stop, even if the game crashes, keep trying, to know if its working, when you press "Sign in" It will bring you back to the account option screen (The acc option screen is where you chose what why to sign in). If that happens, dont stop trying, it will be a short amount of time till it logs you in after you get that sign.
Sorry to say but it will take a long time till it works, but atleast it will work. If you dont close your game after you log in, you wont have to go through this anymore, so its worth it
The Pokemon team is working to fix it but for now, this is the only way to log in (from what I know)