You can tell if the GPS is working by viewing a file- it should have the location coordinates visible as a letter followed by string of numbers and the numbers will change as you're car is moving. It can take a minute or two for the GPS to "lock" onto the satellites so view a file from mid-drive, not at start-up
There is some history involved with the power ports on these cams. When the mount was developed it was for a single-channel cam, so powering through the mount meant it was easier to remove the cam to protect against theft. There was already a power port on the cam and it was left intact rather then redesigning it. In the first version there were issues when powering through the mount so it was re-designed. When the 2-channel cam version came about, the rear cam had to be plugged into the front cam, reducing the benefit of putting power through the mount. Usually it worked OK with power going to the mount but it was soon discovered to be more reliable to have power going directly to the cam. So for all A119/A129 type cams, we recommend power be applied directly to the cam, not through the mount. The GPS in the mount will still receive power this way so nothing is lost.
Phil