I've bought bittrex leonArdo copy and get an mail message that ask me re-download leonArdo. Then what should I do, where is the license key?
The key is built in to the program. So, re-downloading it should get you going.
No, isn't leonArdo message is the privet key you gave is not registered to this product!
Are you sure, you are using the newly download binary? Make sure to delete the old one and use the newly downloaded one.
These mix ups happen from time to time. And make sure you are entering the full key/secret on login.