A quick look at the browser console when viewing your sites shows that your CSS, among other things, is being blocked as it's being served over HTTP rather than HTTPS the rest of your page is being served as.
To fix this, go through your vbulletin settings and make sure all references to your site are HTTPS and not HTTP; if that doesn't work, add a replacement variable in your style editor redirecting HTTP to HTTPS (see attached pic)
Attachment 159111