Grub menu working but hidden, can't make it visible

I had exactly the same problem.

After trying several solutions, one did the trick (explaining with details in case someone else needs it):

1. Edit /etc/default/grub by running in terminal while in the correct folder:

   sudo gedit grub
   

2. Uncomment the line #GRUB_TERMINAL=console. The correct version shall be:

   GRUB_TERMINAL=console
   

3. Save the file.

4. Run in terminal:

   sudo update-grub
   

5. Restart. GRUB menu shall appear now.

Note: I don't know why but graphical terminal wouldn't work. The console is a bit uglier but I don't care.

I also had this problem. Your description lead me to the final solution: GRUB-GFXMODE=auto was the problem.

I entered the GRUB console by pressing C (after I had uncommented the GRUB console output in /etc/default/grub so that the GRUB menu was visible again) and ran the command videoinfo which returned nothing.

Ok, with an automode that doesn't work, any output is difficult ;-) That´s the cause of the problem. The system doesn´t automatically detect the screen resolution. It´s necessary to manually enter a proper value.

I changed to GRUB-GFXMODE=1280x800, which is the known resolution of my laptop, your values may of course differ. Editing the grub file was possible in graphic mode with file manager opened in root-mode (you need root privileges to alter a system file), for the grub-update command I used of course a terminal, as described in Felipe's post.

And finally, I had my beautiful GRUB screen back :-)