Not sure if you're using the KDE or Gnome version, but for KDE I was able to fix it this way just a few minutes ago:
- There's a ying yang symbol on the right-side: click that.
- When the panel opens up, click "more settings" on the right-side.
- When the next panel opens up, click "maximize panel."
I rebooted after doing this and the setting saved through the reboot; so it's not something you should have to do each time you boot it up.