Sorry for the late reply. For some reasons I did not get any notifications in the last few days that there were any new topics posted on here.
I really cannot see why wordpress would tell you that unless you updated the plugin already in the past with a higher version number somehow that is now stored in the database. Very odd…
Regardless, you can simply login at https://support.wp-pizza.com/my-account, download the latest version from there, unzip the archive and overwrite the old files with the new ones.
I would however recommend that you first deactivate (DO NOT uninstall or you will loose all your settings) the plugin ,then overwrite the files and subsequently re-activate
Hope that helps