Inside Trunk release on 2000 Camry not working?

There are at least two choices. First one, the rod is broken or loosen. Depending on the problem you have to either/both replace it and set an appropriate tension. Second one, the lock is broken or by some reason does not want to work properly. If it's broken you have to replace it; if it's stuck you need to put some lubricant (for instance, WD-40).