The key to successfully uploading images is to make sure the jpg file size is small enough to be processed by the website server. Here's a quick way to check the file size prior to upload.

When you click the browse button to find the file to upload, this window appears.

Clicking the top right icon will display a dropdown View menu from which you can select "Details".

Once you've selected "Details" from the view dropdown menu each file shows the file size. Only upload images whose file size is less than 300kb.

Close this window to return to the Photo Gallery Upload page.