In the apache2 error log it says this:
[Wed Jul 31 15:44:13.248391 2019] [php7:warn] [pid 6331] [client 82.221.112.219:63055] PHP Warning: require(vendor/autoload.php): failed to open stream: No such file or directory in /var/www/chossel.club/html/index.php on line 12, referer: https://chossel.club/admin
[Wed Jul 31 15:44:13.248625 2019] [php7:error] [pid 6331] [client 82.221.112.219:63055] PHP Fatal error: require(): Failed opening required 'vendor/autoload.php' (include_path='.:/usr/share/php') in /var/www/chossel.club/html/index.php on line 12, referer: https://chossel.club/admin
[Wed Jul 31 15:44:39.038419 2019] [php7:warn] [pid 6324] [client 82.221.112.219:63057] PHP Warning: require(vendor/autoload.php): failed to open stream: No such file or directory in /var/www/chossel.club/html/index.php on line 12
[Wed Jul 31 15:44:39.038696 2019] [php7:error] [pid 6324] [client 82.221.112.219:63057] PHP Fatal error: require(): Failed opening required 'vendor/autoload.php' (include_path='.:/usr/share/php') in /var/www/chossel.club/html/index.php on line 12
[Wed Jul 31 15:44:39.216806 2019] [php7:warn] [pid 6322] [client 82.221.112.219:63058] PHP Warning: require(vendor/autoload.php): failed to open stream: No such file or directory in /var/www/chossel.club/html/index.php on line 12
[Wed Jul 31 15:44:39.217087 2019] [php7:error] [pid 6322] [client 82.221.112.219:63058] PHP Fatal error: require(): Failed opening required 'vendor/autoload.php' (include_path='.:/usr/share/php') in /var/www/chossel.club/html/index.php on line 12
[Wed Jul 31 15:45:31.279769 2019] [php7:warn] [pid 6641] [client 136.179.37.68:4139] PHP Warning: require(vendor/autoload.php): failed to open stream: No such file or directory in /var/www/chossel.club/html/index.php on line 12
[Wed Jul 31 15:45:31.280231 2019] [php7:error] [pid 6641] [client 136.179.37.68:4139] PHP Fatal error: require(): Failed opening required 'vendo