@RaajRaaj Unfortunately I can't send a screen recording as this is a client SP site.
I am not a tenant admin in their org so I sent installation video and instructions to the tenant admin. The app was installed Version (2024.1.2.1666) and added to all sites. I have created a modern page and added the ArcGIS for SharePoint webpart to the page. I edited the webpart and clicked "continue" to access public content only. I saved the and published the page and saw the error message in my initial post.
All external users using B2B guest accounts are seeing this error message yet the internal users can see the public map inside the webpart.
I asked the tenant owner to create an internal user account for me which they have done and I can see the map, strangely I can now see the map when signed in with my B2B account. I asked them if they had done something with my B2B account but they said they haven't. Yet when I checked with all the other external users they still get the error shown in my initial post.
This seems like some sort of permission issue. The external users have contribute access to the site so it's not a SharePoint site permission issue, I'm wondering if this is some kind of tenant permission elsewhere.
I'm really struggling to diagnose the problem because I only have SharePoint site collection admin rights to the site, I have tenant admin rights and I had to give step by step instructions to the tenant admin to install the app.
