I checked your gallery, and I got this result:
I noticed that under settings -> misc.sharing.addthis_username, you had added your domain name. If you don't have an addThis username, then simply leave this field blank. It might have some negative effect on sharing ...
Also, I noticed you were using Imagevue X2.7.2 ... There were a few updates since then, and at least one targeted towards fixing a small issue with sharing. See updatelog:
https://www.photo.gallery/updatelog/
I recommend you upgrade - Just overwrite all files except your content folder, and your specific theme- and config settings will be retained also, since they are stored in unique files.
Please get back to me after the changes above, as I would like to see how it went ...