It's very unlikely the shifter has failed, given the condition. It's an easy fix. Start with GT85 in the gaps, cable entries and anywhere else you can force it in. Let it soak for a while (maybe half an hour or more), and then work the shifter up and down it's range.The bike looks like it's never been used (no wear on blocks or rims. I wonder if the shifter failed and they never fixed it and thus rode it?
Will try wd.
I suspect paws because I pulled tension on the cable and that didn't do anything while I attempted to change through the gears