Camera HEIC

However if you still want jpg versions:

Select the images in Photos app on your mac,

File>export

Choose kind : jpg

Size : full

Quality : Maximum

Click export, choose a folder to put them in, then upload to shutterfly from there.

According to this, Shutterfly, HEIC is a supported format for at least some of their activities:

https://support.shutterfly.com/s/article/upload-my-photos

Contact Shutterfly support if that’s not working.