Doorbell pro

Hi, my homes not but 6 months old. I bought a reconditioned doorbell pro. Hooked everything up by the books, it powered up, got everything set up and was working fine. Within an hour it stoped working saying low voltage and lost signal. From what I’ve gathered with my doorbell in my home being so mew I wouldn’t need the transformer. Is this so or do I need to order the ring transformer?