Default icons, installed icons and fonts not working in IE11

Hi, I’m hoping I can get help with a problem which has left me stumped for a few days.

I had an SSL certificate applied to my WordPress site after which all my content, plugin instances, fonts and icons disappeared. My hosting company restored the site from backup and all the content, plugin data and images work fine now but the fonts and icons will not work in IE11 though they appear fine in Firefox and Chrome. I have checked on an old setup I have with IE8 and the fonts and icons show fine there.

I had updated to 4.7 so rolled back the site to 4.6.2 from the WordPress release archive with no effect. I also tried copying over the entire site from a backup created before the SSL was applied and the fonts and icons won’t work from that either. I’m working now with the most recent version of my site and upgraded to 4.7.1 this morning. This didn’t fix anything.

I’ve disabled all my plugins to no effect. It also isn’t a caching problem as I’ve deleted the cache and tried on a colleague’s computer. I have two other WordPress sites with identical set ups and they appear fine in IE11.

Oddly when I tried installing a new theme with new fonts they worked fine until I changed the font in customize and they then reverted to default again and wouldn’t maintain any changes. This isn’t just an issue with Google fonts – the WordPress default icons in the dashboard, icons for the WYSIWYG editor and elegant icons have all disappeared. I have Google Fonts and Elegant icons working fine in my other WordPress sites.

The site is hidden from public view so I can’t point to it but I’d appreciate any advice on what to look for, thanks.