Translation:They can set up their business at any time.
I've tried to watch patterns, and some I have noticed, but some???? Just can't figure them out. For this one, I spelled the French "entreprise" wrong by spelling it "enterprise." I can only guess that they marked this particular type-o wrong because my misspell "enterprise" is also an English word. Anyway, be advised "tout le monde" that if you type fast, you are probably going to have some automatic typing of words that are similar such as these and get them wrong.
Yes, there is -- I'd say one phrase can almost be the opposite of the other. "Â un moment donné" means "at a particular moment" or "at a certain point", whereas "â tout moment" here has the sense of "n'importe quand", that is, "whenever/anytime/at any given moment".