Have a read of this thread to see just what can go wrong: https://www.exxosforum.co.uk/forum/viewt ... =18&t=5047
Looking at the picture, the solder doesn't look like it has melted properly (Look at the dull shine and the way it looks kind of squashed), so may not be making good contact. That's suggesting that it isn't hot enough, either because the temp is set too low on your iron or you aren't heating it for long enough. Solder will be completely liquid when correctly heated and held together by surface tension until you remove the iron and take away the heat.
If as you suggest here:
Then the STE is not a good place to practise your skills due to the fragility of the boards, not just from a soldering/de-soldering perspective, but also from a mechanical point of view just from handling, so set it aside and get some cheap electronics kits to practise on from eBay and watch some of the soldering how to videos on YouTube to avoid damaging your board. Be patient, it will pay off, and I'm urging caution because I've made the same mistakes myself over the years.
As for W104, if you have continuity between all 3 pins, that is probably your issue. All 3 jumpers should either be between pin 1 & 2 or 2 & 3, but not all 3. Any STE I work on generally gets the links replaced by jumpers.
