Customize Message Code Not Working

Hello – I’ve installed LoggedIn and added this code (https://wordpress.org/support/topic/customize-messages-2/) provided here to customize the message when someone is logged out of the site due to multiple simultaneous logins; however, the error message is not changing. It still says “There has been a critical error on your website. Learn more about debugging in WordPress.” The page is hidden behind a ‘coming soon’ curtain so you won’t be able to view it, but I placed the exact code into functions.php. Thank you!

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