Just to support pro pixels issue, I’m experiencing this with Firefox also. I get a grey screen with only the rev slider showing up.
I’ve deactivated all plugins and switched themes and can confirm that issue is caused by the Neighborhood theme.
I’m running the latest version of WordPress, WooCommerce & the Neighborhood theme.
In Firefox, the wf-loading class is staying applied to the html tag constantly. I notice in other browsers in which the theme works the wf-loading class is not there, instead there is a wf-active class. The wf-active class is not apparent is Firefox. When I remove the wf-loading class the theme displays the way it should.
It appears you have an error in your js that isn’t removing the wf-loading class from firefox properly.
The version of Firefox i am using is 43.04, across both pc and mac.