I got exactly the same Fatal error. I attempted to install X2CRM on a local Laragon (AMP) server, on Windows 10.
The requirements.php script also didn't find any fatal issues, and the installation was reported as successful.
Then, when trying to access the local site, I got the exact same fatal error.
I found some other threads on this forum, where it was advised that the /protected/runtime directory must have the Writing permission for the user, and that the 'assets' directory must be present, and also with the Writing permission.
I changed the permissions on all of thes