$ mate-panel --help
Application Options:
--replace Replace a currently running panel
--reset Reset the panel configuration to default
Your first choice option is mate-panel --replace, because the --reset option will reset your panel customizations (like panel placement, applets, launchers, etc.).
By default, you should be able to open a terminal with Ctrl + Alt + T if you need a terminal to replace the panel.
In addition to the command for replacing the panel given above, you can also open MATE Tweak and switch away from, and then back to, your layout (if you have saved a custom layout). In the terminal, run mate-tweak to bring the app up.
I'm using Ubuntu Mate 24.10 and consistently experience the loss of the system panel when I unlock the system after it goes to sleep as well as sometimes when I boot the system up or reboot it. I'm getting around this by modifying my rc startup script to initialize mate-panel, but it seems there should be a fix for this. Has anyone else experienced this?
When the panel disappears I use CTRL-ALT-T to launch a terminal, which invokes mate-panel during initialization -- a real kludge, but it does work.