The phrase is "
at no time".
At no time should the participants leave the dance floor, or they will be disqualified from the contest.
At no time have I ever said such a thing.
Contrast with:
He ran very fast and apprehended the thief in no time.
In no time, he (had) apprehended the thief.
I had the job finished in no time at all.
In no time at all I had the job finished.