Error 500 with vendor after updating to 1.7.6.1

[Vivianagr]

Hello,

I get this error since today I did an update from 1.7.2.2 to 1.7.6.1

Warning: include(/public_html/src/Adapter/Configuration.php): failed to open stream: Permission denied in /home/public_html/vendor/composer/ClassLoader.php on line 444

Warning: include(): Failed opening '/public_html/vendor/composer/../../src/Adapter/Configuration.php' for inclusion (include_path='/home/public_html/vendor/pear/pear_exception:/home/public_html/vendor/pear/console_getopt:/home/public_html/vendor/pear/pear-core-minimal/src:/home/public_html/vendor/pear/archive_tar:.:/opt/cpanel/ea-php71/root/usr/share/pear') in /home/public_html/vendor/composer/ClassLoader.php on line 444

Fatal error: Uncaught Error: Class 'PrestaShop\PrestaShop\Adapter\Configuration' not found in /home/public_html/src/Core/Addon/Theme/ThemeManagerBuilder.php:85 Stack trace: #0 /home/public_html/classes/shop/Shop.php(489): PrestaShop\PrestaShop\Core\Addon\Theme\ThemeManagerBuilder->buildRepository(Object(Shop)) #1 /home/public_html/classes/shop/Shop.php(133): ShopCore->setTheme() #2 /home/public_html/classes/shop/Shop.php(413): ShopCore->__construct('1') #3 /home/public_html/config/config.inc.php(119): ShopCore::initialize() #4 /home/public_html/index.php(27): require('/home/...') #5 {main} thrown in /home/public_html/src/Core/Addon/Theme/ThemeManagerBuilder.php on line 85

I can't find public_html/vendor/composer/../../src/Adapter/Configuration.php not even in clean prestashop 1.7.6.1 version.

[Rhobur]

Delete the vendor directory completely and upload the vendor from the 1.7.6.1 archive.