2 common causes are either the keystore not being valid or the jetty.xml not having all the proper settings.
You can verify the keystore with
Code:
keytool -list -keystore /opt/zimbra/jetty/etc/keystore -storepass `zmlocalconfig -m nokey -s mailboxd_keystore_password`
A common missing config item is the zimbraAdminUrl. You can verify that it's present with
Code:
zmprov gs `zmhostname` zimbraAdminUrl