Twirling Circle of Death (images not loading)

I updated to 3.7 two days ago and also took the opportunity to change the images that are in the gallery on my home page. The web address is: https://www.snapdragonfamilyphotography.co.uk

Having done this, all I get now for the images is twirling loading signs ?? I can’t figure out what I’ve done wrong and my post on here two days ago went completely unanswered.

Could some kind soul advise me as to what I’ve done wrong and how I fix it.

Thanks Jane