I can't type special characters on my Mac firmware password request

I have the firmware password enabled on my MacBook Pro. I had never used it until this morning, when trying to access from another partition I have to write it inevitably to be able to do anything; I can't even return to the primary boot partition anymore. The problem comes here. My password includes special characters, such a #. But I'm not able to write that or other characters, which the system allowed me to include when I configured the password.