VIP emails disappear intermittently from mailbox

The email in my VIP box appears intermittently. I have no idea why the emails show up and then disappear, leaving a message that I have 133 unread emails, and no emails visible in the box. I have tried to rebuild the mailboxes, I have turned off program and restarted, I have restarted my computer. Nothing seems to bring those reliable VIP emails back every time I open the mailbox. Help! I need a viable solution to ensure I never miss a critical email.