The German language allows a reordering of most declarative sentences with a subject in the third person (e.g. he, she, it and they) in a way to put Es in front and then the verb. The verb itself keeps its grammatical form.
Regenwolken kommen. => Es kommen Regenwolken.
As you can see, the kommen keeps the form, Regenwolken demands.
This special form is used to put the focus on the verb instead of the subject or any other grammatical part that takes the first place in the sentence, as a verb has to be in the second place in German declarative sentences.
With this knowledge, it is easy to translate the sentence literally:
Es ist noch kein Meister vom Himmel gefallen.
=>reordering=> Noch ist kein Meister vom Himmel gefallen.
=>translation=> Until now, no master has fallen from the sky.