This is a reported bug that is being addressed by the developers.
Missing on Startup
Running this command in a terminal window will bring back the menus for the current session:
$ initctl restart unity-panel-service
To save time and having to:
- Check first to see if the issue is resolved
- Open a terminal Window
- Run the command
I wrote a short script and added it to my startup apps. The script will do all the above. I'll have three minutes to notice if the problem is fixed of which I can disable the startup script once the bug is fixed.
There's a sound notice to nudge me to check if it has been fixed... then finally the command is automatically run.
The menus will be fixed 4 minutes after each reboot.
espeak "Resetting unity-panel-service"
initctl restart unity-panel-service
The script can be added to startup by typing
startup applications in the Unity Launch Search Button.
Disappearing during logged in session
The script above resolves the menu problem that is always missing upon boot. The menu subsequently disappears between boots. When this happens I find the AltCntlT to bring up a terminal and typing
unity as mentioned in the previous answer is ideal for that instance.