Thank you. The issue was the silent requirement that Apple has in order to facilitate sharing of a calendar with another apple user. Apparently if in my Contacts, say for John Doe, I don’t have an email entry and just a phone number and maybe physical address, then iOS considers John Doe “unreachable” to inform John Doe that I have shared a calendar with him. So, in order to share a calendar with a Contact, that Contact must have an email address.
Very unfortunate because the other user could be texted the invitation, or the sharing app could warn that the user does not have an email address and give me a link to share with the other person.
Farzad