I'd stick to DME if you can get that. In a factory sealed bag it will last a decade, possibly longer. Even when opened then closed/sealed properly, it will last years. I have proof of this.
Cans of LME vary widely in quality and age is not in their favor. Some LHBS sell bulk LME, dispensed into a jug or plastic bag from a plastic barrel. If they're busy and sell a lot, it's probably fresh, otherwise leave it, and use DME instead.
Definitely contact the operation you bought he gelled can from and ask for a refund. Or of the whole recipe kit if that's the way it came.
If it's still fermenting you can heat up some DME (with hops if you want) in as little water as possible, chill and add to it. Or just start a new batch.