Here is the screenshot: https://imgur.com/a/agKhut5
There are 30+ folders and over 100+ images that are in that directory where I took the screenshot. But only 4 folders show up. It does allow you to scroll down but its just blank.
The issue is with Firefox and the way the Media Manager is in SP. The media manager works in chrome and worked for a while in firefox but over time ends up doing something like this. But its a recent change that is causing it because I was using firefox and SP for a long time with no issues but something in the last 2 months changed that is causing the issue. JCE and the built in joomla media managers still work, its just the SP media manager that isn't working.