On the character select screen please try to login to a different world server.
You can right click your character and then choose to login to a different world.
This will auto zone your character to one of the three starter cities.
This can help narrow down the issue. If you still can not login, a file check, or a reinstall might be necessary.

First of all, try to narrow down the issue if it is on your PC. Try to use a family or friend's PC to try to login (if they also play the game).