Perhaps you could share what is the model of your thin client? So we can get a grasp of what we’re dealing with.

Good starting points: https://www.parkytowers.me.uk/thin/

I had good results with microwaving a bunch of beads in a microwave safe non-plastic bowl on mid-low.

It drives out the moisture, and you can see the bead colour indicators change.

But be careful, they’re hot!

Looks like one of those recorded message things you find inside greeting cards - the glob of stuff below the black epoxy blob (the ic), looks like a badly corroded button.

Can try cleaning the button up a bit, or removing it entirely, and bridge the connections beneath it.