Error after upgrade to TYPO3 10

TYPO3 Questions Installation
1

Hello,
I upgraded TYPO3 from 9 to 10.4.23. Install-Tool und Backend are running. But when I go to the frontend (https://10.bergzeit-ettlingen.de), an error appears.

Does anyone have a tipp?

Thanks
Leo

(1/1) Error
Class 'TYPO3\PharStreamWrapper\Manager' not found

in /kunden/206180_70794/rp-hosting/7620/8620/typo3cms/typo3_src-10.4.23/typo3/sysext/core/Classes/Core/Bootstrap.php line 463
    protected static function initializeIO()
    {
        if (in_array('phar', stream_get_wrappers())) {
            // destroy and re-initialize PharStreamWrapper for TYPO3 core
            Manager::destroy();
            Manager::initialize(
                (new Behavior())
                    ->withAssertion(new ConjunctionInterceptor([
                        new PharStreamWrapperInterceptor(),
at TYPO3\CMS\Core\Core\Bootstrap::initializeIO()
in /kunden/206180_70794/rp-hosting/7620/8620/typo3cms/typo3_src-10.4.23/typo3/sysext/core/Classes/Core/Bootstrap.php line 101
        // happen errors before we call GeneralUtility::setContainer().
        GeneralUtility::setSingletonInstance(LogManager::class, $logManager);

        static::initializeErrorHandling();
        static::initializeIO();

        $disableCaching = $failsafe ? true : false;
        $coreCache = static::createCache('core', $disableCaching);
        $packageManager = static::createPackageManager(
at TYPO3\CMS\Core\Core\Bootstrap::init(object(Composer\Autoload\ClassLoader))
in /kunden/206180_70794/rp-hosting/7620/8620/typo3cms/dav-sektionen-10/index.php line 25
// Set up the application for the frontend
call_user_func(function () {
    $classLoader = require __DIR__.'/vendor/autoload.php';
    \TYPO3\CMS\Core\Core\SystemEnvironmentBuilder::run(0, \TYPO3\CMS\Core\Core\SystemEnvironmentBuilder::REQUESTTYPE_FE);
    \TYPO3\CMS\Core\Core\Bootstrap::init($classLoader)->get(\TYPO3\CMS\Frontend\Http\Application::class)->run();
});
at {closure}()
in /kunden/206180_70794/rp-hosting/7620/8620/typo3cms/dav-sektionen-10/index.php line 26
call_user_func(function () {
    $classLoader = require __DIR__.'/vendor/autoload.php';
    \TYPO3\CMS\Core\Core\SystemEnvironmentBuilder::run(0, \TYPO3\CMS\Core\Core\SystemEnvironmentBuilder::REQUESTTYPE_FE);
    \TYPO3\CMS\Core\Core\Bootstrap::init($classLoader)->get(\TYPO3\CMS\Frontend\Http\Application::class)->run();
});
2

Is that a composer mode version or legacy mode?

If a class is not found, you should take a look at the autoloader (if composer, do a composer dump. if legacy dump autoload files in install tool).

3

Thans for your response.
The problem was an old “vendor” folder…