Galaxy 4 Watch Will Not Turn On

I've got a Galaxy Watch 4 Classic that will not turn on following a software update. The standard magnetic clip-on charger does not appear to charge it, and when I attempt to charge it on an Ubiolabs Qi Charger that I use regularly for my Galaxy S9+, I get an amber flash on the indicator light - "FOD Detected." Still does not appear to have any effect on the watch.

Doing the Two-Button Hold to try to reboot the watch doesn't do anything. I'm guessing the watch is completely drained, and will not charge up again for some reason. Anyone seen this before, with Galaxy Watch 4 Classics, or other Galaxy Watches, perhaps? I'd love to attempt a repair before giving up and buying a new watch to replace this one.