If nothing changes at all, the glass may be etched. Etching happens when soft water, too much detergent, very high dishwasher heat, or repeated washing gradually wears down the surface of the glass. Etching is actual damage, not buildup, so it cannot be reversed. The glass may still be perfectly usable, but it will not return to a truly crystal-clear finish.
5. The exact low-effort soaking method I use