There are two spots to check:
1. Under your profile -> edit. This is where you can enter your address to receive your zaps. Seems like you have that part sorted.
2. To send, you need navigate wallet and connect your wallet via Nostr Wallet Connect.
If it’s still not working, I would try another Lightning wallet for payments like Coinos and see if that works.
You can always send up a bat signal to the nostr:npub18m76awca3y37hkvuneavuw6pjj4525fw90necxmadrvjg0sdy6qsngq955 team.