having trouble adding photos to shared albums

I recently spent a good portion of my day creating several shared photo albums. Family sharing is turned on on all my devices (1PC, 1 ipad, apple TV, iphone 6 and mac).

Some of the albums have photos in them. However...not as many as I thought I was sharing to that album. For instance, a cruise I created an album for had upwards of a hundred pictures and only 10 of them made it to the album. I have since tried to go back and add photos. I open photos, click on "shared", see the album I created and click the "add photos or videos" link. Then I select the photos and hit the add button. A little circle shows up on the top left, and when it completes it's round, I figure that means it is finished transferring those photos to the album. But....no. Still only 10 photos in the album. I thought, maybe if I close photos and reopen, they will show up. Nope. I am going to reboot my mac next, but not sure why this is happening. I have also gone into photos, clicked a few pics and clicked the share button, picked share to icloud, and picked the album I had created. Still no more photos in the album.

Clearly I am doing something wrong but am too dense to know what. I would appreciate any help you smart folks can give the old lady.

I am doing this on my mac running El Capitan.