Cell Protection preventing unlocking Open File Read only protection bug or not?

I just recently was trying out “Open File Read Only and Record Changes Options in Optios/Security” for the first time and it wound up greying out the check marks and I couldn’t enter the password to unlock. My limited searches via Google looking for a fix didn’t come up with anything that helped. I managed to find out that after looking through the menu’s that “Cell Protection” was checked and then unchecked it and after that I could unlock the Read Only option ithe security tab. Is this a bug?