The 500 internal error may originate from two things, the first is user error (client-side issue), and the second is that there is a problem with the server. To resolve the issue try the following :
1. Refresh or Reload the page using key F5 or Ctrl + F5.
2. Clear Cache & Cookies
3. Deactivate all the plugins. Third-party plugins and themes can easily cause 500 internal server errors.
The above steps should most likely resolve the issue. If these steps do not resolve the issue. It not, please contact Customer Support at 800-547-5417