Both applications were installed and when attempting the upgrade process failed. My data was being sync'd with OneDrive. The Windows store app literally failed seconds after the import process started.. when the app was relaunched it prompted me to send a note back to the developers (which I have done several times) and then the application appeared to have created a new vault with no data. There were approx 125 records in the vault mainly login data..
I have managed to work around this now by reinstalling v5 and re-keying all my data into v6. I then re-installed the windows app and sync'd against the new vault. not really my plans for new years eve..