Memories not syncing between iphone and mac

You cannot edit memories on a Mac.

But you can create new memories from albums.

Instead of editing an existing memory, select all photos in the Memory, create a new album, then rearrange the photos in the album - add new photos or remove the photos you do not want.

• Select the album in the sidebar, then click Show as Memory.
• Scroll down to the bottom of the photos, then click Add to Memories.

Now you have an edited version of your Memory and can delete the previous version of the memory.

As to the syncing of memories: Enjoy your Memories in Photos - Apple Support

Make sure that your iPhone, iPad, or iPod touch is running iOS 10 or later and your Mac is running macOS Sierra or later.

If you want to get the same Memories on all of your Apple devices, follow these steps:

1. Set up iCloud on all of your devices.
2. Sign in to iCloud with the same Apple ID on all of your devices.
3. Turn on iCloud Photos on all of your devices that you want to use with Memories.
4. Update your Apple TV HD to tvOS 10 or later.

That should ensure that all new memories will sync between the devices, but I could not find any documentation by Apple about edited memories. It is not clear, if edits to the memories are supposed to sync between devices.