iCloud "Unable to delete items" Server error
iMac (21.5-inch Mid 2011), OS X El Capitan (10.11)
I started using Flickr because it was recommended and my 5GB of iCloud storage was getting full with backups, photos and such. I was attempting to create more room by deleting PhotoStream photos. I thought the correct sequence was to turn off iCloud PhotoStream on all my iOS devices and my iMac so the photos wouldn't attempt to be re-created wirelessly while I was trying to delete them. Then I manually delete all the necessary photos in iCloud.com. That's when I ran into the server warning problem.
Your answer got me thinking (well it's about time Pilgrim) - I activated PhotoStream in Settings>iCloud on all devices (OS X and IOS) and the went to my IOS devices first to use the iCloud>Manage Storage>iCloud Photo Library>Disable and Delete to let the server do it's thing. Then I went to the iMac System Preferences>iCloud and unchecked the PhotoStream radio button. Then did the same on all OS X and IOS devices for the family sharing etc. Then turn off Settings>Photo & Camera>iCloud Photo Library on the IOS devices. I'll check back in 30 days to see if the photos deleted in iCloud .com.
Thanks for getting me started
Try signing out/in to iCould.com to see if you can reset the connection to the server.
iCloud "Unable to delete items" Server error