Facebook Share variable result

I am using Tiny Frame as my theme and have installed Addtoany for my social links. I currently don’t have a live site, just working on localhost on my PC at the moment.

I’ve added the Facebook share but it gives variable results which I don’t understand.

On my first page (either set up using first page template or as a standard page) clicking on the FB share button results in the Facebook share popup displaying Share on Facebook
https://www.addtoany.com/add_to/facebook?linkurl=http%3A%2F%2Flocalhost%2Fmysite%2F&linkname=West+Yorkshire+Therapy+Centre+%7C+Hyperbaric+oxygen+treatment+for+multiple+sclerosis&linknote
Clicking on the displayed Share button bring up another popup with “Facebook – Addtoany and the link https://www.addtoany.com/add_to/facebook?linkurl=http%3A%2F%2Flocalhost%2Fmysite%2F&linkname=West+Yorkshire+Therapy+Centre+%7C+Hyperbaric+oxygen+treatment+for+multiple+sclerosis&linknote

However on other pages I get the brief “connecting to Facebook message then the expected “Share on Facebook” Localhost and the url LocalHost which is what I’d hoped for.

I’ve placed the Addtoany share icon in a widget area at the bottom of the pages

What is going wrong with my first page?

I should say I am very, very new to WordPress and everything linked with it and coding, at the moment, is a complete black art which I’m trying to avoid at all costs if I can help it.

Any help, gratefully received.

https://www.ads-software.com/plugins/add-to-any/