If a contract is between a person and an LLC that no longer exists, then of course the contract would no longer be enforceable. However, if an LLC is forfeited temporarily because of an error in not submitting certain paperwork/fees etc., and that error is corrected in a normal/reasonable amount of time then its likely that the contract would still be enforceable.
However, if the contract was between say a person and a company name, without the LLC, and the company continued to operate, simply not as an LLC any longer, the contract might still be enforceable.
You will probably get better answers if you give the backstory.

