iCloud photos not transferring to all my devices

Read this article iCloud Photo Sharing - Apple Support

Before you begin

1. Update your iPhone, iPad, or iPod touch to the latest iOS, your Mac to the latest macOS, and your Apple TV 4K or Apple TV (4th generation) to the latest tvOS.
2. Set up iCloud on all of your devices.
3. Make sure that you’re signed in to iCloud with the same Apple ID on all of your devices that you want to use with iCloud Photo Sharing.

Then follow the upcoming steps in the article .

Also see this article Transfer photos and videos from your iPhone, iPad, or iPod touch - Apple Support

Try going to iCloud.com using a computer to see if the items are there and whether they are from the device or the computer. That should show whether the device or the computer isn't syncing. If the computer, try going to System Preferences/iCloud and stop syncing. Wait a couple of minutes, then recheck syncing. If the device, go to Settings/Your Name/iCloud and do the above. As a last resort, you can also try signing out of iCloud and then sign in again.