I have the JJC JF-G2 Flash 3in1 kit. My receivers are both on, same channels, but one does not sync with the transmitter. I've turned everything off, replaced batteries, changed channels, turned everything back on, and still the transmitter only syncs one receiver, the other (same one still) turns on, but does not sync. I got them as a Christmas gift, 2016, so wear and tear, I wouldn't say, shouldn't come into play. Can anyone help me?
If one works and the other doesn't, I'd suspect that it's just defective.
On their website, JJC says:
Consumers are God. JJC have set up a perfect after-sale service during years’ development. Now we have the excellent after-sale service center. We always supply local and professional service to our customers.
This seems positive; I suggest contacting them to see what they say.