Multiple PHP versions are usually installed on most servers.
You enable a specific PHP version by using a .htaccess directive, usually an AddHandler or a SetHandler directive.
If this directive is missing from the .htaccess file, the default PHP version of the server will be used.
In most cases, the "default" PHP version is an ancient one, e.g. PHP 5.3 which I suspect is the case with your server.
Putting your site in Emergency Off-line Mode replaces the .htaccess file. The new .htaccess file does not have the AddHandler / SetHandler directive.
Since the default PHP version of your site is too old, it cannot understand the code it sees and throws an error.
You should go to your hosting control panel AFTER enabling the Emergency Off-line Mode and select the PHP version you want to apply.
Nicholas K. Dionysopoulos
Lead Developer and Director
🇬🇷Greek: native 🇬🇧English: excellent 🇫🇷French: basic • 🕐 My time zone is Europe / Athens
Please keep in mind my timezone and cultural differences when reading my replies. Thank you!