I must say thank you very much for your response and eagerness to assist.
After playing around with Moodle for some time I realized that I had the "Buttons Course format" installed but somehow the upgrade broke that plugin. After reinstalling the plugin the app was able to work flawlessly.
So just a word of advice for Moodle Admins out there, ensure and reinstall the "Buttons" plugin after a major upgrade if you had a previous installation of that plugin.
Thank you again Juan, the response was much appreciated.