Checking old seeds: Do the germination test for plant seeds. If stored for too long or improperly, the seeds lose their ability to germinate.
In many cabbage plants, the radicle roots appear after just two days. For carrots, on the other hand, it can take up to two weeks. If hardly any seeds have germinated, you should get new seeds. Otherwise it's simply not worth the effort. If at least half of the seeds sprout, then the seeds can be used again.