Linguini theme photo issue

I installed a new theme (Linguini from Themeforest). I love it BUT, I can upload photos to the media library, but when I try to post them in the slider, posts, pages, etc. The images don’t appear. I get a perpetually spinning circle (loading?) and a little “pizza box” in the upper corner of the photo space.
This only happens on computers in my house. Desk top and lap top. The site works fine from computers elsewhere and even from my iPhone.
I called internet provider but, because other sites I have work just fine, they say it’s not their issue…..even though the only place it fails is here.
I’m pretty much stumped. Any ideas? I’m far from a computer tech so keep it somewhat simple, please.