From time to time warmane wants me to put in generated code to log in because i have 2 step authentication on. First code never works, it says it expired. Than i try again, i get no email. Then i try couple more times and i get 5 emails at once. I dont know wchich one to use. I use one it doesnt work. I put password again and it sends me another. I try it but it says its invalid. I do it until i have too many entries and i have to wait until "later" to log in. Your system sucks.
If it does not work with first 2 tries, wait a few minutes and try again. You should always use the last code you receive. But if it was received earlier, wait for new one.