Why am I gettting the following error and how to check if the directory exists?

I have a new webhost and they told me that this particular panel is pretty good but it is not cpanel, does anyone know what kind of a panel this is? I am also getting the following error and just wondering how I could check if the folder exists or not? because I can't find the folder called var?

Warning: session_start(): open(/var/cpanel/php/sessions/ea-php73/sess_5bc77575be1faa655411e0eb9ef76535, O_RDWR) failed: No such file or directory (2) in /home/pianocou/domains/pianocourse101.com/public_html/header2.php on line 3

Warning: session_start(): Failed to read session data: files (path: /var/cpanel/php/sessions/ea-php73) in /home/pianocou/domains/pianocourse101.com/public_html/header2.php on line 3

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