Q: Can't share calendar on Wife's iPad

It is OS X Calendar and family sharing with my wife is enabled.

If I click on Calendars at the bottom of iPad Calendars, this particular calendar (details of a long European tour) does not show up.

If I go to my wife's iCloud account the calendar is there and if I try to resend the invitation, it tells me (on the Mac) that it is already subscribed.

There must be something wrong when Safari fails to come up with the "Accept" option because I, then, do not get the "Inbox" on Calendar

Just to clarify the above:

I receive the email invitation on my wife's iPad and click on "Join Calendar"

Safari immediately tries to open a tab entitled: "Calendar Share Reply", but it just stays as a grey page.

My recollection is that on other devices, this page gives me an "Accept" option which, when clicked, then opens the Inbox on Calendar

When I open my wifes calendar on her iCloud, the calendar that I am sharing is there.

I don't share music or movies (we have different tastes!) and I have cleared all browsing history and cookies on my wife's Safari, so still a mystery.

I don't use Safari very often and that was not ticked on my iCloud.

No, it is not even listed, but it is all there on my Wife's iPhone!