Business Card QR codes do not work with iPhone

The vCard feature on InDesign's QR code generator is fixed at v2.1, which is old and does not properly encode upper ASCII characters (such as accented letters). Other problems with the iPhone code reader have been reported with increasing frequency; it would seem that Apple's implementation is moving further and further from this old standard.

The only real solution, and the recommended one, is to use the plain text mode to structure and encode v3 (or v4, if you insist) vCard and other data types. The ID tool works very well in this mode and your data is completely safe from scraping or collection by "free" web services.

There are also resolution issues; the grid should be at least 1mm and preferably a little larger even with high-resolution reproduction. If you're packing in a lot of data (making a fine grid) and then reproducing it at a small size, iPhones in particular seem to have trouble resolving  them (but all devices and scanners need a minimum clear resolution, anyway).

This primer has pretty much all you need to know: https://nitrosyncretic.com/DPR/dpr_qrcodes.php

Happy to answer any questions it might leave you with.