As a test I've done the following:
Installed Enpass in a Virtual Box.
Synced a test vault with a remote WebDAV server.
Downloaded the synced files from the WebDAV server to my local computer.
Deleted the files from my WebDAV server.
Destroyed the Virtual Box along with Enpass and all such data.
One of the downloaded files is named "vault.enpassdbsync" and all the others end with ".enpassattach".
In an attempt to recover the test vault on my local computer I've done the following:
Created a new vault.
Named it "test".
Selected "Backup File".
Chose the file "vault.enpassdbsync".
Entered my password.
Enpass said, "Incorrect Password."
How do I restore vaults that were synced to a WebDAV server then downloaded locally?