@PeterSkrzyniarz Thank you for sending me coins and replying, though I can't still find the transaction. As you said, I checked my account and got a message saying I must make an outgoing transaction, so I changed my account info spending 1 BURST, which I had received from someone 4h ago (not sure who it is).
Now I got a public key and started mining successfully. Maybe, my account has been activated.
Anyway, thank you so much.