Both photoshop and paint.net export works fine.
There is only one thing what you have to do is in photoshop to add an alpha channel and change that.
I gave you the explanation earlyer in this messeage but i think you you missed it.
with the alpha channel you control the transparency of the glass
if you don't adjust the alpha channel, the glass is too dark
my send example from the glass has the alpha adjusted
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Making alpha channel photoshop.zip
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So inport the png file in Photoschop and adjust the alpha and export it as DDS file