Error: Failed to initialize WebGL

Can anyone help me understand why I am getting the above error on one particular website page?

The page is a Route Builder and has a left hand column (which DOES flash up for a split second before disappearing) and a right hand map pane which does not appear.

I am left with a completely blank page.

The Develop > Show JavaScript Console results in display of a series of :
3 off "Error: Failed to initialize WebGL." with lots of detail
"Error rendering page"
and finally "Failed to load resource".

The site provider asked me to toggle WebGL 2.0 but this makes no difference.

A friend with what appears to be same OS/Safari versions BUT a DIFFERENT GPU (AMD vs. my Radeon) has no problem.

I have content blockers off, extensions disabled and VPN disabled.

Help...!

Thank you.
Further: if I DISABLE JavaScript the page loads but without the interactive map element. So still unusable but seems to be JS issue?

My MacBook works fine, so this suggests AMD Radeon Pro 580 issue - any thoughts?

Error: Failed to initialize WebGL
 
 
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