Got it working. I emailed Anker. What wasn't apparent to me is that I needed to hold down the button on the SoundSync for about 5 seconds to get it to power on. Then I was able to connect - with the power bank, and also another older, smaller battery.
btw, I do sometimes use Google Maps as a quick & easy GPS. I prefer the full one for certain longer trips, with all the extra info I get off a good Garmin GPS, and also when I travel outside the country and might have more limited data available.