Peer Status Unknown

We rebooted our VOIP phone system now some of our peers are showing status unknown while other peers came up fine and show status OK. What info can I give you to help me, I’m new with Asterisk. I have version Asterisk (Ver. Thank you

Are they dynamic hosts? If so, they have not yet registered.

Thanks for your quick reply David. It shows hosts as dynamic in the extension settings. Also when I did a sip show peer the peers that are unknown have expire: -1 and the ones that are ok have expire: 1650