Examine the vacuum cleaner and determine what sort of thing is wrong. Is it not turning on? Is it not staying on? Is it vacuuming weakly or unevenly? Is it leaving fuzz or other debris behind? Is it tripping a circuit breaker? Is it producing a noise or an odor as it runs?
Verify that your vacuum cleaner is plugged in and turned on, and that the electrical outlet has power flowing to it. If you don’t have a circuit tester, try plugging in a lamp or radio that you know works. Yes, it’s obvious, but without electricity, your vacuum cleaner isn’t going anywhere.