Pokémon Go crashes when I try to login

Don't worry about your account; all your data is stored server side and will be restored. I personally swapped to a new phone and could keep playing from where I left off just fine.

Firstly, make sure you've completely rebooted your phone to clear out any active apps and try launching Pokémon GO with no other apps running just to make sure this isn't an issue about having too little memory available.

If that doesn't work here's what you can do to completely reset every bit of data for Pokémon GO which should hopefully make it able to launch again (I doubt what you have is a hardware issue since the S6 is a very high-spec phone which shouldn't have any issues rendering the game).

The following instructions should work for any phone running Android 6 Marshmallow.

1. Open the settings app.
2. Tap the menu item called 'Apps' or 'Applications' (This name can differ between devices; ex. the Nexus 5X says 'Apps' and the Samsung Galaxy S6 says 'Applications').
3. Specifically for the Samsung Galaxy S6: Tap the item called 'Application Manager' to show your installed apps instead of the default Samsung ones.
4. Find the item named Pokémon GO in the list and tap it.
5. You should see the app name and icon at the top and a list below. Tap 'Force Stop' at the top.
6. Now tap storage from the list below.
7. You should see two buttons, 'Clear Data' and 'Clear Cache'. Tap 'Clear Data' ('Clear Data' should also clear the cache).
8. Tap back once to return to the menu where you can see the 'Uninstall' button and tap it.
9. Pokémon GO should be completely uninstalled with all of its data removed too. Go to the Google Play store and download it again.
10. Attempt to login using your preferred account, it should launch.

What this process is attempting to do is clear every single bit of data related to Pokémon GO from your phone since sometimes an app uninstall won't completely remove it.

If this doesn't work, please comment.

Without a crashlog or backtrace it will be impossible to know what could be causing the crash. Even with the logs it might be difficult for an end-user to identify the cause of the crash, as the log may need to be symbolicated, etc.

I would open a ticket with Niantic by reporting an issue signing in. There is also a report a bug form, but I feel that this is specifically a log in issue, so the first link would be your best bet.

A simple solution to this is - Log out and again Log in to the game.

But since you're already logged in and the game simply crashes on starting, here's something you can try:

1. Uninstall the current Pokemon GO App from your phone.
2. Download the latest version from the Play Store and install it.
3. Run it. Log in using the Google Account.

I too once faced this problem and following the above steps solved it for me. Good luck!

Since there is no log of any sort. I would suggest clearing cache of google play services. because google play services is the app that deals with logging in to a google+ account in the game.

If this does not open then try Venoda's solution if you haven't already tried. I think after clearing cache of both app will resolve this issue.