This issue occurs if your monitor resolution is set too low. Please make sure that your monitor is set to a resolution as high as possible.
On Windows 7 or Windows 8, right click on the desktop and choose "Screen Resolution", then adjust the resolution in the window that pops up.
On Windows 7 or Windows 8, right click on the desktop and choose "Screen Resolution", then adjust the resolution in the window that pops up.
On Windows 10, right click on the desktop and choose "Display Settings", then adjust the resolution in the window that pops up.
The minimum resolution of the game client is 1024 x 768. If you are able, set the resolution to 1600 x 900 or higher. If you are running on 1366 x 768 resolution, you will need to move your Windows Taskbar from the bottom of your screen to the left or the right edges.
Once you successfully log in as your character, you may go to in-game Options to change your resolution.