Thru-Axle forks and hubs are much better for bikes with disc brakes than are traditional hollow axle hubs because Thru-Axle hubs ensure perfect alignment of the disc every time you install the wheel. But with a dynamo hub, there's a catch. Standard hubs with Thru-Axles don't require the skewer to be as tight as it would need to be on a traditional hollow axle hub. The skewer only needs to be tight enough so that it doesn't come loose while you ride, whereas a QR in a hollow axle hub must be tighter, lest the hub work its way out of the dropout. So cyclists with Thru-Axle hubs quickly get used to installing the skewer less tightly than they would with a hollow axle. This can cause trouble with a dynamo hub.
If the dynamo hub is not held tightly in the Thru-Axle dropouts, the hub will vibrate a bit and the axle will rotate. If it rotates enough there will be stress on the wires and the spade connectors embedded in the axle. Either the wires or the spade connectors will be damaged, and no power will come from the hub.
When you first install your SON Thru-Axle hub, carefully notice the orientation of the connectors. Perhaps align them straight down if possible, with the wire then looping around and up the fork blade. Ride for a few minutes with the lights on, or with your phone charging. Then stop and notice if the connectors are still pointed straight down. If they have rotated a bit clockwise, you'll know that your skewer was not tight enough. Make the skewer tighter and do the experiment again. Once you have the skewer tight enough so that the connectors never rotate, you're good to go.