Registration seems to work only with lowercase chars.
Just use an online converter for your eth address, and you can join the airdrop.
http://google.com/?q=convert+to+lowercase

Luckaly I have mine finally confirmed now after few failed attemps
Good luck everybody!
This free online case converter tool convert your text from uppercase to lowercase, lowercase to uppercase, title case, sentence case, proper case, inverse case, normalized with single space and normalized with double space in a single click.
Try these helpful websites,
https://unitconverter.net/case-converter/