This is because for the moment my app only supports keysend. Contact your wallet provider and ask them to support the only truly peer to peer lightning protocol that doesn't rely on censorable things like DNS
With that said my app will eventually support zaps as soon as an acceptable solution to the metadata "messages/boostagrams" is solved
For now the only wallet solution is alby, though I hear that coinos has finally implemented keysend support but I haven't tested it yet.
