There’s an issue with 5.7.11, would expect an update will come out fairly soon. You should be able to fix right now by rolling back to 5.7.10.
Also have a bunch of sites with issues after 5.7.11 upgrade. For reference in my case
– frontend and backend are still viewable
– but no ACF (flexible) content shows on the frontend
– no errors thrown in error logs or via wp_debug
– reverting to 5.7.10 fixes the issue