In Linux Hosting, For security reasons few vulnerable modules & functions are disabled.

To avoid any hosting accounts hacking, we have disabled this function.

For eg. Ini_set() function is essential for Joomla to Run.
Now, to overcome.
Just create a custom php.ini on the websites root folder and add the 2 lines on it.

session.auto_start=off
suhosin.simulation=off

Save it and try refreshing the URL.