Recently Google has disabled the ability to use Google synchronisation feature for all 3rd party browsers. So there is way to enable synchronisation if you turned it off or try to set it up after clean install or in a new browser profile.
Good news :) Sidekick sync is coming soon.
We've started development of our own secure synchronisation logic in advance and are going to release in one of nearest updates (ETA June 2021)
This new feature will allow all Sidekick users to sync data between Sidekick browsers installed on different machines securely and easily. All the data will be encrypted on you local device before it is sent to synchronisation server so nobody can get or read your data except you.
I need my history and bookmarks now, is there any workaround to import all my data?
If you had synced all your data and after reinstall or on a new device you can't get it back, you can try following steps to get your data.
Along with Sidekick Install Chrome browser on a same device.
Enable synchronisation in Chrome browser (it should work)
Wait until all your data is synced
Open Sidekick browser and quit Chrome
In Sidekick go to chrome://settings/importData
Select proper Chrome profile and tick the data you want to import
Done! Your bookmarks and history will be imported from your Chrome browser, so you can continue using Sidekick. However, take into account, that the data will not be synced until we release an update with the sync feature.