htaccess redirect issue

Long story short, I want to redirect a few old pages and also use a simple html page instead of the 404 Wp error page but I cannot.
I have this in my htaccess file:
“ErrorDocument 404 /404.html
RewriteEngine On
RewriteBase /”
just above the Wp default code which is unaltered. However, everytime I try to access a non-existent page the same, default, Wp error page loads. The redirects (not posted) don’t work, either, showing the same Wp error page.
Why I cannot use my code in htaccess? I don’t have any issues with other scripts on the same server.
Thanks!