Prestashop is behind http proxy firewall

[retechp]

I have searched pretty extensively, and this is the only thread that seems to come close to my issue, but I am unsure where to go from here with this information. 

 

Our Prestashop installation will be used internally; however, it runs VERY SLOW. I have discovered that if the PrestaShop marketplace module is enabled, the back office manager is VERY SLOW. 

When I disable the back office module, PrestaShop is FAST!

I also determined that because PrestaShop is behind a proxy firewall, it is somehow being blocked.

Is there anyone who can guide me through to a resolution?