That's strange! It's 'normally' the other way round ... all other browsers can except IE!!!
But, a suggestion. On a Mac, using FireFox, install Web Developer Tools.
https://developer.mozilla.org/en-US/docs/Tools
Now don't get scared ... we are NOT gonna ask you to develop anything! ;) We're using the tool to gather info ... that's all!
Once installed, start FireFox. Before you hit your Moodle, launch from the Tools menu of browser, Web Developer, Network. That will popup a smaller window and as you 'surf' it will show what files, etc. are being transferred from the site to your machine.
You might see some errors for js files that are needed to build the Auto editor Tool bar.
IF you do see errors, take a screen clip of that Web Developer Tools Network window, edit it to blacken out any sensitive info, and then come back here and post. Don't really know IF we can solve the issue but without some more info, we're all taking stabs in the dark! ;)
'spirit of sharing', Ken