Laravel composer autoload/ guzzlehttp : fatal error

When deploying my laravel website (1&1 mutualized), this is the fatal error I get:

Fatal error: require(): Failed opening required '/homepages/41/d623699018/htdocs/athyr/athyr - copie/athyrcopie/vendor/composer/../guzzlehttp/psr7/src/functions_include.php' (include_path='.:/usr/lib/php7.0') in /homepages/41/d623699018/htdocs/athyr/athyr - copie/athyrcopie/vendor/composer/autoload_real.php on line 66

Already tried : 'composer update' 'composer dump_autoload' and I checked it's PHP 7 everywhere.

Thanks in advance for your precious help.

Stephanie

via Chebli Mohamed