Have you tried a different cord? I've come across some cords with smaller than normal plugs...still "1/4 in" but slightly smaller that didn't work at all well with the jack in my active bass...
If it's just a bent jack, it should be an easy fix. You can unplug the amp, let it sit for a little while (5 to 10 minutes), pop the top off and see if the contact of the jack is visible and needs to be pushed back to where it belongs.
Clubs - EMG 3, Frankenbass 3, Mesa/Boogie 4, Squier P 5-String Club 17, MIM P-Bass 108, Lefty Union 184, Tricked Out Squier Club 185, Avatar 205, MarkBass 228, Hartke 291, Squier Owner's Club, SX