I assume that this is not a freshly placed (from library - not favorite) window in a fresh project from the default template?
You must have scrambled your attributes. The windows, like all library parts and elements, look for attributes such as materials by the index number, not the name. So, apparently you have a wood material occupying the index number position that the window expected to find the glass material.
If the parameter does indeed say 'glass', though, then your glass material must have been customized and messed up. Open the materials settings for that particular glass and examine the settings.
Cheers,
Karl
One of the forum moderators
AC 28 USA and earlier • macOS Sequoia 15.2, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB