I know this is advice that you may have heard from many people, but I will give you this advice:
Do not use yobit because they are a very shady exchange and have altcoins that do not have a good future, I used yobit in the past and bought many altcoin (shitcoins) that today have no value and are no longer listed in yobit, I had many losses. You should also take into account the fact that yobit is anonymous
We already suggested for a hundred times about yobit but these people do end up not to listed and still uses up this shady exchange until to this day.
If he do have a coin thats being only listed on Yobit then you dont have any choice but to risk it up to sell on that place but be prepared on high chances to experience problems along the way.
I cant still believe that this exchange was still alive upto this year.
In regards with the problem the code has been sent out on email which you would need to copy before logging in.It clearly shows that op miss out to input such code
and trying to log-in directly.It isnt a bug.