I had the same problem recently:
The “forgot/lost password” function simply did not work. But when i had disabled all plugins for experiments on my site, i noticed that it worked at once. Then I saw that it had actually works all the time, but it was just linked wrong.
The correct link is “https://<Your-Domain.com>/wp-login.php?action=lost password“. A plugin changed it in “?ac=lostpass” (wrong!). When I disabled all the plugins one by one, I discovered that the problem was the plugin “User Dashboard” by anildhiman.
The solution:
Disable / delete the plugin “User Dashboard”. After that, it works properly again.
If that does not work, simply try to disable all plugins and check if it works. If it works then, the cause of the problem is a plugin.
Best regards
