Thanks for writing in.
It depends, was it previously in Dropbox or OneDrive? If yes, then you have to remove it and re-add it from the local drive. We've retired the third party sync APIs and switched to Folder Sync for all local vaults now. That means you have to download Dropbox or OneDrive clients to sync the data to your local drive and you can then ask 1Password to sync from that directory.
Keep in mind that 1Password 6 does not support local vaults and the feature is limited to helping with migrating the data to a 1Password.com account.