Login page not working

Greetings.
When trying to Login, user simply put Username/email and password and after clicking “Login” the page simply refreshes and returns empty, as if login was unsuccessful. Since I have a page with content restriction, it is possible to verify effectively that login was not successfull.

I have made one more test: I deleted the cache (I have WP Fastest Cache) and anfter that login seems to work correctly.
So it seems something related to cache adn WP Fastest Cache.

Any help – thanks!

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