I've attempted to use browser.storage.sync with a private, Mozilla-signed extension, but cannot get it to work. Are there any reasons why it shouldn't? To be specific, I've done the following steps * Modified https://github.com/mdn/webextensions-examples/tree/master/favourite-colour to use browser.storage.sync instead of browser.storage.local. * Added an application ID to the manifest * Submitted the addon privately to AMO * Installed the addon on two computers signed into a Firefox Sync account * Attempted to save sync data and sync it Problem: The ostensibly synced data is not downloaded to the other computer. Here's what happens on computer 1: * Data is stored in storage-sync.sqlite * Syncing completes successfully * After syncing, the sync log says: 1503422223251 Sync.Engine.Extension-Storage DEBUG Syncing extension settings for ["sp33dk0r3@gmail.com","favourite-colour-test@extensionsynctest] 1503450912632 Sync.CollectionKeyManager INFO Setting collection keys contents. Our last modified: 0, input modified: 1503414144602. 1503450912632 Sync.BulkKeyBundle INFO BulkKeyBundle being created for [default] 1503450912632 Sync.CollectionKeyManager INFO Processing downloaded per-collection keys. 1503450912632 Sync.BulkKeyBundle INFO BulkKeyBundle being created for savepage-we@DW-dev 1503450912632 Sync.BulkKeyBundle INFO BulkKeyBundle being created for printedit-we@DW-dev 1503450912633 Sync.BulkKeyBundle INFO BulkKeyBundle being created for sp33dk0r3@gmail.com 1503450912633 Sync.BulkKeyBundle INFO BulkKeyBundle being created for favourite-colour-test@extensionsynctest 1503450912633 Sync.CollectionKeyManager INFO Clearing collection keys... 1503450912634 Sync.CollectionKeyManager INFO Saving downloaded keys. 1503450912634 Sync.CollectionKeyManager INFO Bumping last modified to 1503414144602 * In storage-sync.sqlite, the record for key-colour changes from created to synced. The last_modified field is updated. Here's what happens on computer 2: * The log says only Syncing extension settings for ["sp33dk0r3@gmail.com"] * storage-sync.sqlite does not get a new record for favourite-colour-test@extensionsynctest * I can use the extension to save a colour to storage-sync.sqlite - in that case, the log proclaims that the data is synced to he cloud. However, it is not downloaded to computer 1. Additional troubleshooting steps: signed out and back into sync account on both computers. Deleted weave folder and storage-sync.sqlite. Reinstalled addon. So the question is, is this not supposed to work? Thanks for any help!