only html shows on pages not css

[flo99-rgb]

I used softaculous to install ph7builder. The web pages only show the html and not the css formating.

The server log shows:
PHP Warning: require(/home/visi85002848/public_html/WEBSITE/folder/_protected/app/Bootstrap.php): Failed to open stream: No such file or directory in /home/visi85002848/public_html/WEBSITE/folder/index.php on line 39

index.php shows at line 39:
require PH7_PATH_APP . 'Bootstrap.php';
$oApp = Bootstrap::getInstance();

How is this fixed?