This issue pertains to double or triple-pane insulated glass units (IGUs). These windows rely on a vacuum-sealed airspace filled with inert gas (like argon) to provide insulation.
Here’s a clear, helpful post for a blog, forum, or social media: can a window be resealed
The exterior or interior caulk between the window frame and your home's siding or drywall has cracked, shrunk, or peeled away. This issue pertains to double or triple-pane insulated
Before starting, you must diagnose exactly where the window seal has failed. Perimeter Seal Failure (Frame to Wall) helpful post for a blog
Vinyl or aluminum frames that have warped from heat or foundational shifts will never seal correctly.