In order for the files to be read correctly ensure they are all labelled as .jpg and NOT .JPG
Should I resize my photos before uploading them?
Resizing your photos before uploading them will speed up the upload and count less towards your storage/usage count. If you plan on offering digital downloads and would like to offer a high-resolution download, we recommend resizing your photos to 5000px wide before uploading them. If you are not planning on offering digital downloads, we recommend resizing your photos to 2400px wide before uploading them.