I’ve found the root of the problem and it was causing multiple errors.
#1 – Not even being able to perform a simple SELECT query via phpMyAdmin.
#2 – A plugin that we use as a Catalog for our products was not displaying the products (probably due to a large query function)
#3 – And Finally, the menu tabs from being displayed.
The solution? Although we are running on a Dedicated Server on HostGator(having virtually unlimited space), the tmp dir of the ROOT was maxed out at 4GB. Emptying it out was able to fix almost everything.