Syncing takes places via iCloud using iCloud Drive. On your iOS device go to
Settings -> Apple ID, iCloud … (right at the top) -> iCloud
and make sure that
After enabling iCloud, iCloud Drive and granting chargEV permission to access iCloud Drive, it may take a while until your favourites and charge cards are synchronised.
If you find this hasn’t worked for you, get in touch with ChargEV Support.