Same issue for me – works perfectly on Chrome and IE, but all uploaded fonts render in system default when opening in Firefox. I’ve disabled all pop-up/ad blockers, etc., and tried the disable/reenable method. Can you please share your response to the OP or advise if there’s something I need to do on my end? Thanks!
BTW – I have another domain (www.pcmsvcs.com) using WordPress with the UseAnyFont plug-in, and it works correctly in Firefox.