Cant drag Time Signature to score

First Time user and loving it, but one small snag ... I've got a score that's in 4/4, but I can't drag the 4/4 symbol into the score. Just for testing, I tried dragging a different time signature to the first measure, and the music reconfigured itself to the new time signature as it should, it's just the actual time signature that's not showing up. Surely I'm missing something simple. Thanks