Sounds like a GFCI (ground fault circuit interupter) outlet has tripped and won't let you reset it. It could be because the outlet itself is bad, or because the GFCI is actually detecting a continual fault, and that by not allowing you to reset it, it's actually doing it's job of protecting you.
If you havee the knowledge, turn off the breaker at the service panel that powerss the circuit iin question. Then you can pull the outlets downstream of the GFCI and inspect them and their wiring. Work your way back to the service panel.
If all looks good, you can pull the gfci outlet and wire-twist the hots together and the neutrals tgether that were in the GFCI box. Then supply power to the circuit. If it works fine, then it may be the GFCI that needs replacing.
Wiring is not terribly difficult, but it can be terribly dangerous. If you feel uncomfortable poking around in a box, then certainly look for assistance.