Calling into a meeting

For some reason, our meeting invitations are not showing a phone number to call into.  It used to and now it doesn't, so either a setting got switched off during an upgrade so something is really wrong with our account.  Where can I go to see if there is a button or tab that needs to be turned on?  And if it does need to be turned on, will the already created meeting link show the phone number if I copy or email the invitation?  Thanks!