Session_start(): open(/usr/local/php7/lib/php/session/...) failed: Permission denied (13)

hello after clean install i have this error
Whoops \ Exception \ ErrorException (E_WARNING)
session_start(): open(/usr/local/php7/lib/php/session/sess_s8dq41jnq2r8cmrkn47gur2li3, O_RDWR) failed: Permission denied (13)

Doesn't look like a Grav issue. The folder in question is your main PHP folder. Do you have other PHP software that uses sessions working on this server? The error message is telling you exactly what the problem is. You don't give any information on the hosting environment.

here the site
https://flexicontent.org/documentation/