There is a 15 second delay with that model I hear before it will turn itself on (another person said 30-45 seconds after the TV is on). And it can only be turned on with the remote (or by the HDMI connection). And did you check the remote battery (CR2032)? Even though you can see the IR with a camera, if the battery is too low it might not function correctly.Well my sound bar didn't work with the remote. It is the correct part number and using a camera that can see IR the remote appears to work.
Maybe that's the reason that the previous owner disposed of it.
Another person said after their iPhone was updated to iOS11, it stopped working by Bluetooth between the Samsung and the iPhone. Although once they updated the firmware on the soundbar too, then it was working once again.
Another person said theirs died after 1 year and 2 months.
It can connect to the TV by HDMI, Bluetooth, or optical cable it looks like. The woofer and the soundbar has their own power connections. And I don't think you can use the woofer without the soundbar. It is also supposed to turn itself on and off by the TV if you use the HDMI connection.
Hope something here helps, if you haven't been here yet.
https://www.amazon.com/Samsung-HW-J450-Channel-Wireless-Soundbar/dp/B00TKPAWFO