I have a WordPress and everything seems perfectly fine but I have this page that has title 77% and it shows error 404 page. How can I fix this? I am kind of sure it is because of the % in the 77%. The permalink uses the 77 but for some reason wordpress still doesn't like that % in the title. What can I do to fix this while keeping the % there?
There is nothing you can do, the % symbol is not a neutral character and whatever 2 characters immediatly follow it are used to represent a character. This is called percent encoding.
For example, to encode a % you would use %25.
Thus the answer is:
No, it is not possible to fix this while keeping the % there, because URLs are percent encoded.
Should by some stroke of luck you manage to get it working, I would recommend still avoiding it due to the misuse of the % symbol