Work Folders feature was introduced in Windows Server 2012 R2 that allowed clients to synchronize files with a built-in agent (in Windows 8.1 and 10, there’s also a patch for Win 7 Enterprise), later they’ve also added support for iOS and Android. To read more about Work Folders: https://technet.microsoft.com/en-us/library/dn265974(v=ws.11).aspx
By default you can only create 21 Sync Shares in Work Folders, because of limitations in the JetDB which Work Folders is based on. Usually a few Sync Shares should be more than enough for a company of most sizes and extending the limit beyond 21 will only be necessary for very rare occasions. Due to the rare nature of the environment I would need up to several hundred Sync Shares and reached the limit quickly. When reaching the limit you are able to create more Sync Shares but users that has their Sync Share configured to one of those created after number 21 will receive “Parameter is incorrect” error in their Work Folders Control panel.
In order to extend the Sync Share limit beyond 21: Open Regedit on the Work Folders server, navigate to HKLM\SYSTEM\CurrentControlSet\Services\SyncShareSvc\Settings, create a new Multi-string value with the following data:
..and that’s it. Restart the Sync Share Service and every Sync Share you create will work until you reach 1024 Sync Shares on the same server/cluster. Make sure to configure all nodes with the same configuration if you’re a cluster.