Glass not transparent

I am making an scène with an window and i assigned an glass material to the glass. But it didn’t look like glass. So I put a red cube to test if you could see it through thr glass. But you can’t. Material settings:

IOR: 1.1
roughness: 0

Oh it works, I lowered the IOR, but i dont get it, because 1.1 should be low enough

Does that glass have thickness? Or is it just a flat plane?
Never use refractive materials with geometry that is physically impossible.

Screenshots, .blend file? Or are we supposed to enter in the few settings you’ve mentioned onto a random mesh and hope we have whatever results you’re having that we also can’t see?

I wanted to Add a photo but it doesnt worked for me, and Now the glass works. Thanks!