Where are you getting your cert from? Your going to have to give us more details if you want anyone to be able to figure out what your doing wrong.
For what possible reason would you want to use a wildcard cert for the webgui? How many possible fqdn/IPs could you point to the web gui?
The web gui should be accessed by limited number of users. Create as cert with your own ca, have the users that will access it trust your ca. Put in whatever SANs you want to access it by. Done - set the cert to be good for 10 years. Never have to deal with this issue again.