You may find that a contact with an old iPhone is unable to save your vcard (.vcf) to their iPhone before iOS 13.

This means that when they start downloading your card, their iPhone will not offer to open the card in their contacts after they have clicked on "Save", but in "Files", for example.

The iPhone should suggest opening the Vcard in "Contacts".

If your contact is experiencing this problem it's simply because they have deleted the "Contacts" application from their iPhone and will have to download it again.

To do this, they need to go to their App Store and search for the 'Contacts' application (direct link here from the iPhone), download it and open it.

All that's left is to try downloading the Vcard again.

Two scenarios:

1 / If the iPhone still suggests Open in "Files", go to "Options" then look for "Copy to Contacts", the Vcard will open and all you have to do is click on "Save".

2 / If the iPhone directly suggests Open in "Contacts" then click on it and once the Vcard is open click on "Save".

You can check in the phone book to see if you can find the contact's Vcard by searching for it by name or company name.