Sign message (with your btx address that's holding btx). Type AIRDROP in capitals.
Copy the signature you get and submit it to the website.
Yes. Thanks. I already tried this. Used both the GUI and the Console (the Signed message is the same in both places). I use validateadress command and got the pubkey. Entered both of them in the website. Still this error... Do I need to have a specific amount in the wallet (BTX)?