If you’re still encountering sign-up difficulties or other problems in Pokemon GO, you can rest assured that the development team is still on the case. Niantic has been working to fix the known server issues, which aren’t as prevalent now and haven’t been affecting all players. You can expect Pokemon GO to launch in more countries once the issues have been tackled. Pokemon GO is now available in the U.S., Australia and New Zealand for iOS and Android devices.
Pokemon GO development team still working to fix server issues
Pokémon Blog 