Miraculous signs that some today claim to be able to perform are false. There were only twelve apostles (Paul, not Matthias was God’s choice—but that’s a blog for another time). And there was a way of identifying them—see 2 Corinthians 12:12:

The signs of the true apostles were performed among you with great patience, by signs, by wonders and by supernatural works.

The miracles (literally, “powerful works”) created wonder in those who beheld them and, thereby became the signs (evidence) that the one doing them was an apostle.

Now, if I told you that my church was located in a home on such and such a street, and that you’d have no problem identifying it because there was a sign on the front lawn with the words, “Such-and-such Biblical Church,” you’d be utterly frustrated upon seeing the same sign on the lawn of every building on the block.

A sign identifies. It sets something or someone apart from other things or people. Paul said that miracles (supernatural or powerful works) are the sign of (or the way to identify) a true apostle. Since there are no more apostles, then there are no more identifying signs. And since there are no more such identifying signs, there are no more apostles!