GIF Transparency

[RogerH57]

Hi

I am totally confused as to why I have suddenly started finding that saving a GIF with transparent background is now replacing transparency with white?

Even if I simply create a new document with "Background Content" as Transparent, Add a shape, then [File]  [Export] [Save for Web (legacy)] choosing GIF and selecting tickbox for Transparency I end up with a GIF with White background.

If I toggle the Transparency tickbox in the 2-Up Save for Web window the lower preview will switch between a White and Transparent background as one would expect.

I am using Photoshop 24.1.0 on Windows 10 Home Version 10.0.19045

[Abambo]

Do you have screenshots?

[RogerH57]

[RogerH57]

Screenshots provided 10 days ago

Any thoughts?