BNF stands for Backlink not found. It means that when Monitor Backlinks crawled the website it couldn't find a backlink.
If you imported a link, but Monitor Backlinks was not able to find the link, then it could also show BNF.
Monitor Backlinks might not be able to find the link for many reasons:
- the backlink doesn't exist anymore on the site.
- the backlink changed its location on the site
- you imported the link with a typo