Reset the PHP using in PHP version selector in Cpanel. It might be showing already 7.2 or higher, but switch it to different version and then back again to PHP 7.4. You might have deleted the php.ini file while trying to update.I attempted an update and received the following message.
Composer detected issues in your platform: Your Composer dependencies require a PHP version ">= 7.2.5". You are running 5.6.40.
I can no longer access the app.