Step-1:
Delete the existing feeder-id from /etc/piaware.conf & /boot/piaware-config.txt by following command:
sudo piaware-config feeder-id ""
(No space betweeen two quotes “” in above command)
Step-2:
Delete feeder-id from /var/cache/piaware/ by following command
sudo rm /var/cache/piaware/feeder_id
Step-3:
IMPORTANT: Restart piaware for changes to take effect
sudo systemctl restart piaware
Step-4:
While loggedin to your Flightaware account, visit this page and follow instructions to claim a new Station number
https://www.flightaware.com/adsb/piaware/claim
For insight (Optional):
For Beginners - Piaware Feeder-id Mechanism