Is the airdrop registration at
https://bitcore.cc/airdrop.php currently broken? I get "Error: BTX public key (your address) or signed message not valid" even though my signed message is valid (I have done similar message signing for Byteball, which worked fine).
The website says "Address (public key)" which is confusing, but it just means an address, such as 1C8BRHdqCuKwm8ZLmFhiFM3FyFJPyAkRdj, right? (That's not my address, just an example; and my address has more than 1 BTX on it currently, though I don't think that matters.)
And the message to be signed is just "AIRDROP" (without the quotes), right?
Public key and public address in Bitcoin and crypto are often used synonymously, even though technically speaking it is not the same.
We opted for the way the majority of people uses these words.
Did you copy your complete signed message, including the "=" at the end?