It’s an Ortizan S3 wireless speaker. The first two purchases (another make & model, then the first version of this one) both failed to charge properly (or were damaged or faulty in some other way). The one I got last week (before I sent it back to Amazon for replacement) showed the red charging light, but failed to turn on afterwards.
It has its own USB-C cable. First device I plugged into the charger plug I use for my Samsung phone (yes used the included cable), rated 5.0 volts. Second device I simply plugged into my computer, with again zero luck. I don’t want to fry this one too. So where should plug it, then?