What happened to the AddThis buttons? Facebook, Twitter etc?

In certain configurations, the AddThis buttons fail to appear at the foot of every page. These are the buttons that allow you to click through to Facebook, Twitter, Pinterest etc.

So far as we can tell this only happens with the Safari browser on some (not all) iPads.

We've tried everything we can think of to fix the issue but so far without success.

The problem does not exist on most iPads (so far as we can tell), and neither does it occur on Safari on iPhone. And it does not affect Chrome, Edge or Firefox browsers.

And all desktop browsers appear to be fine.

It appears to be related to Apple's enhanced security measures to counter cross-site tracking and other possible exposures.