No Custom field in Screen Options on WordPress version 4.5

@pixelink Studio: Is this option missing from the Edit screen for a “regular” Post or Page, or are we perhaps talking about the Edit screen for a Custom Post Type?

(What I’m getting at here is that the option will only be available if the post type that you’re trying to edit supports Custom Fields; so I’m wanting to confirm exactly which post type you’re trying to edit in this case.)

@girlieworks: this option missing from ‘Screen option’ both on Post and Page. You know usually wordpress has screen option that you can tick hide or show on the top right corner. On previous version of WordPress. the custom field option is there, without any plugins to install.

@pixelink Studio: Do you have any plugins installed on this site (particularly ones which might affect Custom Fields, such as the Advanced Custom Fields plugin)? And if so, have you tried deactivating all of those plugins to see if the option shows up again after that?

@girlieworks: I have few plugins but nothing like ACF (Advanced Custom Fields). I inspect on the browser, there is no custom fields coding of whatsoever.
I had tried to re-install WordPress but still not working.

@pixelink Studio: Did you actually try deactivating all of your plugins? (That’s not clear to me from your last response.)

@girlieworks: Yes, i did and still didn’t work. Any .php file should i change?

@pixelink Studio: Which theme are you using? Have you tried switching to a theme like TwentySixteen temporarily to see if that option becomes visible then?