We recently setup our Web2 server and are trialing with users. It worked when it was just me testing it but since distributing to a few more people no previews load. On pdf we get "undefined" on .sldprt we get "Sorry, no thumbnail preview available for this files (...path/file.sldprt)."
I have combed through permissions and no user group works when it did a few days ago.
I have tried other browsers out of desperation and no difference.