Amazon Photos Sync became unsupported. To reenable the functionality on windows do the following:

C:\Users\YOUR_USER\AppData\Roaming\Amazon Cloud Drive

There should be a “amzn1.account.XYZ-settings.json” file. Open it in a texteditor and change the “AppMode”: “Backup” line to “AppMode”: “All”, and add the path to the sync location on your drive e.g. “SyncPath”: “D:\\Amazon Drive”. I restarted the app and sync was enabled and worked again.

{
  "DeviceSourceId": "pWOUi2BDHKBQWDqkSPY-JoFyHO88NiCTE",
  "DelighterTrackingTime": "2020-08-26T12:49:26.650235-07:00",
  "AppMode": "All",
  "SyncPath": "C:\\Users\\dave-\\Pictures\\amazon",
  "OnboardingVersion": 2,
  "LastSentBackupMetrics": "2025-04-07T14:31:23.6038159-07:00",
  "HasBackfilledHiddenNodes": true,
  "AccountFeatures": {
    "enhancedSearch": 1,
    "familyArchive": 1,
    "basicSearch": 1,
    "groups": 0,
    "groupsInvitation": 0,
    "bulkFaceManagement": 1,
    "faceManagement": 1,
    "stories": 0,
    "thisDay": 0,
    "carousel": 0,
    "thisDayCollage": 0,
    "unknown": 0,
    "devicePersonalization": 0,
    "upsell": 1,
    "voiceSearch": 1,
    "amazonPrints": 0
  },Copy