Apple watch 4 not powering on

Hi Simon,

I really hope you bought the watch because you really wanted an Apple Watch rather than wanting to hone your repair expertise. Apple Watches are notoriously non-repairable; there are really only three parts that are user-replaceable - the display, battery and force touch sensor. Everything else is sealed up tight and/or encased in epoxy and cannot be repaired without specialized equipment and expertise.

So really, you're pretty much down to replacing the battery and/or the display and hoping one of them fixes the problem. Since it's 1/10th the price of a new screen, I'd start with the battery and see if that works; if not, then a replacement screen is about all that's left to try.