Please Help With Robots.txt error

Hello everyone please I'm in an emergency

My blog has two variants the www and non www
the www has a robots.txt file that allows search but recently my non www robots.txt had a disallow request for index and crawling and since then my ranking has started dropping.

Now I've tried editing the robots.txt file from my Yoast but it doesn't change from the /robots.txt extension I went into root and deleted the robots.txt but nothing changed with the robots.txt file at this location(/robots.txt ) please what's wrong or how may I fix this?

use a httacess file in the root .