I get a v1_retired error message when trying to sync with Dropbox

Dropbox retired their v1 sync APIs recently and so any older copy of 2Do using the older sync APIs will stop working. You may see a variation of 400 errors, consistently every time you try and sync. Solution: You need the latest version of 2Do on your device. Current versions: iOS = v3.9.87, Android = v2.6.62 and Mac = v2.3.970

1) First, we would advise you open Settings > Manage Backups and create a new backup. Select this backup and email yourself a copy. This will ensure your data is safe and can later be restored if the need arises.

2) Upgrade to the latest version of 2Do on all your devices (iOS / Mac / Android). 2Do adopted the latest v2 sync APIs earlier this year.

3) In case it still does not work, or you were already on the latest version, please unlink and relink your Dropbox account from sync settings.

Some affected users have reported that unlinking and re-linking as not worked. Another way around this would be to unlink 2Do from your Dropbox account. Please click here to learn how to do this. Unlink all devices using 2Do. Once you have done this, launch 2Do and setup sync again. Close settings and sync manually (by pulling down on the task list to refresh it, or on the mac from the File > Sync menu). Select Replace local data when prompted.

Older devices and OS versions: Please bear in mind that 2Do may no longer be compatible with your OS version or device. There is no way to rectify this. Manufacturers have stopped supported older devices and newer apps require newer features in newer operating systems to function properly. We still support several years older operating systems (Android 5.0, iOS 10.0, Mac 10.10) but that's as far as we can go. Apologies if you are affected by this. You will need to contact Dropbox to request them to enable v1 support for your account as a last resort. 

A note about updating 2Do: All upgrades of 2Do so far have been for free. Simply updating your copy and syncing again should have you up and running again. If app store is showing you a buy now button, log out and login back into it with the same account you used to purchase it and try again. Lastly, tapping buy now will still not charge you given iTunes recognizes older purchases and will prompt you with a confirmation that you have already purchased it and so the update is free. 

The only time this won't work is if you have moved between countries. iTunes does not transfer older purchases and forces users to buy again. This is an iTunes issue that you will need to take up with them.