If you connect Vault with an AEM 6.1 Forms J2EE instance, it fails with the following error:

Connecting via JCR remoting to http://<server>:<port>/lc
[WARN ] Authentication required to access repository descriptors
[ERROR] checkout: Unable to mount filesystem
caused by: javax.jcr.RepositoryException: OK 
caused by: org.apache.jackrabbit.webdav.DavException: OK


When you connect to the J2EE instance of AEM Forms, you need to provide the full path to the JCR Root as follows:

vlt --credentials admin:admin co --force http://<server>:<port>/lc/crx/server/crx.default/jcr:root/