Converting meeting to webinar after account was upgraded

Hello, I have an existing meeting that I want to convert to a webinar.  The meeting link was created before the account was upgraded to support webinar.  I did a test meeting after the account was upgraded and can see the link to convert it.  However, the meeting which was created before the upgrade does not have the convert to webinar.  How can this problem be resolved so that I don't lose the original meeting link?