Hello,
I would be happy to help!
Images can take a long time to download the first time you sync because there are so many of them, and it can take even longer if you have a slow connection.
Please check your media sync status:
If your media sync is idle and you are still missing images, please reset local changes: How to Reset Local Changes
You need to keep Anki open while everything is downloading. If you close Anki, the download will pause, but it will resume once you open Anki again with an active internet connection.
This extended sync time and need to keep Anki open only apply to your initial sync since you are downloading everything for the first time.