Restrict Possible Usernames - what is wrong in this

Can someone tell me why this is not working ? /^[a-z][a-z]+\d*$/ig

I think your regex does not allow for a password that starts with a character followed by a number like: R2…, all your passwords will be limited to starting with 2 characters like: Re… Thus, I think its one of the reasons why it fails.

Try removing the global flag – there’s a known issue with this causing regexp challenges to fail.
Once you do that, you should be able to pass most of the tests, but you might want to think about whether it is always necessary to have two alpha characters at the start of the string (which is what you are currently testing for)