Modern versions of Microsoft Edge run in Enhanced security mode by default. This mode does not support WebAssembly (WASM), which is required by the Sketchfab viewer.
To fix this, in Microsoft Edge, go to Settings → Privacy, search, and services, then find the section called "Enhance your security on the web".
Be careful, as there is another very similar-looking section called "Tracking prevention", but that is NOT the one you're looking for.
You can turn off enhanced security mode completely, but this is NOT recommended as it may open your browser to privacy and security vulnerabilities.
Instead, you can go to Exceptions and add [*.]sketchfab.com to the exception list. This way, your browser is still protected by Microsoft Edge's enhanced security mode, but the Sketchfab viewer will be allowed to load.
Sketchfab does not use third-party tracking scripts or cookies, so your browsing experience on sketchfab.com will remain protected.