How to make the windows material transparent so that I can see an image through it? I created a room (floor, table, walls and windows). For the windows' faces, I used a material with the following features (I list below only the features I changed, the remaining ones kept standard, ie, as they came):

Principled BSDF
Base color: white
Specular: 0.15
Roughness: 0
IOR: 1.5
Transmission: 1
Emission strenght: 0

I checked Screen Space Reflection both in materials and in Eevee render.
Finally, I added a reference image with sky and trees to be the outside environment. However, I cannot see the image through the windows (either in material or render mode, independently of rendering in eevee or cycles).
My question is: How to make the windows material transparent so that I can see an image through it?
When using transparency in EEVEE, make sure to set the material's Blend Mode to something other than Opaque. Alpha-Blend or Alpha Hashed should work fine. For some objects, you may also find things look better if you also enable Backface Culling: