Basic 21

So I know the structure of table and follow known whitepaper. But when I try to read usernames I don't get any conv error and literally can't progress further. I can't understand what I am doing wrong.

There are some subtle differences between the white paper and the challenge, it's not a direct step by step guide.

To my understanding I should get username first and then password using this name, but the query which should get me that name do not prone any errors. I am sure it's a correct query and I think there shouldn't be any issues with syntax, so I am at complete loss.

If it's not producing an error and you're sure its correct, then check for an extra whitespace at the end of your injection. If it's still not producing an error, then it's probably not correct.

You could always post your injection here if you're still lost,