Hi Paul,
So sorry, it seems I had a moment of dislexia!
I am not seeing the icons in the add-ons of the frontend editor of SPPB: SP Page Builder > Pages > frontend editor
Take for example the "Home" page, click on the front-end editor and then click on any of the add-ons. It's there where the icons are not appearing.
I tested using Safari, a browser I never use, as well as my wife's computer, where I have never accessed the admin side of my website. In both cases, the icons for the add-ons are not showing.
Thank you for your continued help,
Hector