The response back from paypal says:
Security Header Not Valid.
This means the API Credentials are not correct.
Double check the API Credentials in your account and make sure you have them entered correctly
If you click one of the settings categories like gateway credentials, it will popualte correctly and allow yo to make changes, For the initial display, I will need to look into the wa_settings table, in the private message section, please provide site control panel access so I can get to the database to troubleshoot.