Here are a few simple things to try when you have a sync issue:

Verifying: If there is an issue reported with syncing, e.g., broken structures or missing manifests, you should first verify the sync data to see if it's intact and consistent. The results of a verification will be reported in the log window.

Cleaning: If the verification fails, you can then clean the sync location or database to remove the sync data in that location. The results of the clean will be reported in the Log window. After a successful clean, you can upload the database(s) again. And just to ease anyones' mind, cleaning a sync location has no effect on the local databases on your devices. Sync data is not your database and is separate from the local databases on your devices, Mac and mobile.

Before you clean sync data: Isolate one syncing device and do the maintenance there clean. Before you do, disable the sync location or specific database on the other syncing devices. After the clean and resyncing is finished, you can then enable the sync location on the other devices again.

To verify or clean sync data, open Sync settings. These commands are essentially the same but are applied to either an entire sync location or a specific database.

Both these actions can be used at any time, for preventative purposes or just to get a fresh start with syncing. Also, you may see unwanted databases in the Remote section of the databases list for a sync location. Cleaning the location will remove these databases too. But if you want to keep the sync data for your current databases, you can Control-click and clean specific databases in the Remote section.

Bonjour syncs are generally transparent, but it can only be used on a local network that allows Bonjour traffic and non-standard ports. Many public networks disallow this kind of traffic to protect their customers. Also, corporate networks will often disallow this traffic for security reasons.

If you find yourself on a network that disallows Bonjour syncing, it is possible to connect your iOS device to your Mac via your Lightning cable. This creates a simple ad-hoc network that will allow Mac-to-mobile syncing. If you are in a corporate situation, please discuss this with your IT department to ensure you're not violating any security policies. They may also issue an exception for a specific port you could use for Bonjour syncing. If they do, you'd enter it in the Port section of the Bonjour options.

Since your devices are generally signed into your Apple ID, using iCloud for syncing is the easiest to set up. However, it should be understood it can only be used for personal syncing. Collaborative syncing is not possible unless all participants are sharing an Apple ID.

If you are using an iCloud (Legacy) sync, the data is synced locally first. iCloud processes will then upload the changes to Apple's servers and propagate the information about it to all other devices. It generally happens smoothly and in the background but it means you can't expect the changes to be ready on other devices as soon as DEVONthink has finished synchronizing to iCloud. If you are using a CloudKit sync, DEVONthink deals directly with Apple's servers.

Here are a few things to check:

Our support for WebDAV services allows you to use cloud services that are WebDAV-enabled. This also presents some self-hosting opportunities, even with some NAS devices. However, they can sometimes be technically more difficult to implement. Here are some things to check:

Dropbox is our longest supported sync method and is generally reliable and a good performer. However, there are a few things to consider.

According to Dropbox' rules, you cannot sync across user accounts. They don't allow you to share the Apps folder or its subfolders between accounts. Also, they only allow our sync engine to be logged into one Dropbox account at a time. If you have a work and a personal account, you can only sync to one with DEVONthink.

Collaborative syncing may be possible using a common Dropbox account, i.e., using the same username and password for syncing. But again, you can only sync to one active Dropbox account at a time.

I enabled the sync and nothing's happening: Our sync engine will not sync, upload or download, without being told to. We believe in opt-in processes whenever possible. Merely enabling a sync location just sets up a location to be ready to receive and transmit data. You need to enable individual databases to sync. You also need to do this on each device you want to sync. If you have enabled databases to sync, check Window > Log for errors.

I'm seeing a message about an invalid encryption key: When you set up a sync location, you have the option of entering an encryption key. This is used to scramble and descramble the sync data so it's stored in an encrypted state. Once you've synced the first time, this value, even if you aren't specifying a key, is stored for that sync location. This value must be entered on other devices syncing with this sync location.

You can't add, remove, or modify the encryption key value for a sync location after the first sync. If you want to make a change, you must clean the sync location first. Disable the sync on all devices but one, the clean the location. After, the clean, Control-click the sync location again, choose Show Info, and make the modification to the key. After the first sync, this will be the value stored for the location. After the clean and resync from the one device, you must change the value on the other syncing devices, then re-enable their syncs.

I am seeing a message about missing manifests: Missing manifests are bits of transactional sync data that cannot be located by the sync engine. When this occurs, it can't validate the information about what has been synced. This is not an issue with the databases; it's missing sync data. See the Verify & Clean section above regarding verifying and cleaning the sync data.

It's telling me I have a duplicate database UUID: As noted in the glossary, a UUID is a unique value given to all DEVONthink databases. If you copy and rename a database file in the Finder, this UUID is preserved and DEVONthink sees two databases with the same UUID. This will not sync correctly. Please contact our support team for assistance on resolving this.