Thanks for your answer, Brian. We found that the problem only existed if links were sent to specific people. We disabled iMessage as you suggested, created new message threads, and eventually checked within the individual address books. We noticed the phone numbers in the "send to" options had turned green for some people. We discovered that within their own address books, their phone numbers were gone. We trust that the people involved didn't edit their own address cards and remove their own phone numbers. They are all in some way associated with software development. We suspect that this had something to do with the transfer of data during the update to iOS 17, and if it happens to other people, they should check their contact phone numbers.