In the short term, I’d recommend you File>Export your collection with media+scheduling included in the computer version, then AirDrop it over to your phone. When you open it in AnkiMobile, it should import any missing media files.
Once AnkiMobile has the files, please sync AnkiMobile, and it should send the media files to AnkiWeb. Once that’s complete, it might be worth syncing the computer again to see if you still get those errors.