I replaced the old factor radio with a used one because the old one's lcd display was blacked out.

The car has the original phone.

Before removing and replacing the radio I forgot to disconnect the battery.
After replacing the radio, radio worked fine but I had strange thinks happening with the antenna. First, the antenna would stay on even after the car was turned off. Somehow I got the antenna to go down.

Now when I start the car and turn on the radio, the antenna does not come up.

Where do I begin diagnosing the problem?

Thanks.