After Installing its can not clear the Cache. Frontend workd, backend not.

CRITICAL
Message: The parameter "postfinancecheckout_payment.plugin_dir" must be defined.
Time: 2019-04-01T09:20:02.083871+0200
Channel: core
request:
{
"uri": "/backend/",
"method": "GET",
"query": {
"module": "backend",
"controller": "index",
"action": "index"
},
"post": []
}
shop: No shop data available
session:
{
"userId": "50",
"roleId": "1"
}

Sorry =)

Shopware 5.6.2 Plugin Versionen was 1.0.49 now 1.0.50 same loosing template.
Same in Twint, Postfinance.

Textform Log****************

Ups! Ein Fehler ist aufgetreten!
Die nachfolgenden Hinweise sollten Ihnen weiterhelfen.

[327C1CCD-2552-3C65-5AFE-4FCBE258B70D] You are not allowed to access the resource 'document/template/payment/invoice.twig'. in custom/plugins/PostFinanceCheckoutPayment/vendor/PostFinanceCheckout/Sdk/lib/Service/TransactionService.php on line 1359
Stack trace:
#0 custom/plugins/PostFinanceCheckoutPayment/vendor/PostFinanceCheckout/Sdk/lib/Service/TransactionService.php(1283): PostFinanceCheckout\Sdk\Service\TransactionService->getInvoiceDocumentWithHttpInfo('4639', '4291615')
#1 custom/plugins/PostFinanceCheckoutPayment/Controllers/Backend/PostFinanceCheckoutPaymentTransaction.php(212): PostFinanceCheckout\Sdk\Service\TransactionService->getInvoiceDocument('4639', '4291615')
#2 engine/Library/Enlight/Controller/Action.php(192): Shopware_Controllers_Backend_PostFinanceCheckoutPaymentTransaction->downloadInvoiceAction()
#3 engine/Library/Enlight/Controller/Dispatcher/Default.php(478): Enlight_Controller_Action->dispatch('downloadInvoice...')
#4 engine/Library/Enlight/Controller/Front.php(228): Enlight_Controller_Dispatcher_Default->dispatch(Object(Enlight_Controller_Request_RequestHttp), Object(Enlight_Controller_Response_ResponseHttp))
#5 engine/Shopware/Kernel.php(185): Enlight_Controller_Front->dispatch()
#6 vendor/symfony/http-kernel/HttpCache/SubRequestHandler.php(102): Shopware\Kernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#7 vendor/symfony/http-kernel/HttpCache/HttpCache.php(448): Symfony\Component\HttpKernel\HttpCache\SubRequestHandler::handle(Object(Shopware\Kernel), Object(Symfony\Component\HttpFoundation\Request), 1, true)
#8 engine/Shopware/Components/HttpCache/AppCache.php(256): Symfony\Component\HttpKernel\HttpCache\HttpCache->forward(Object(Symfony\Component\HttpFoundation\Request), true, NULL)
#9 vendor/symfony/http-kernel/HttpCache/HttpCache.php(238): Shopware\Components\HttpCache\AppCache->forward(Object(Symfony\Component\HttpFoundation\Request), true)
#10 engine/Shopware/Components/HttpCache/AppCache.php(99): Symfony\Component\HttpKernel\HttpCache\HttpCache->pass(Object(Symfony\Component\HttpFoundation\Request), true)
#11 shopware.php(122): Shopware\Components\HttpCache\AppCache->handle(Object(Symfony\Component\HttpFoundation\Request))
#12 {main}

ill load plugin with filezille and Binary transfer method and after activating for Plugin get this error.

After the plugin is installed and the required details (SpaceID / UserID / AuthKey) are entered and the plugin is activated. I get when synchronizing each time this message. Although I have already activated the plugin several times and reloaded the page. The plugin I have also completely deleted several times and reinstalled...

Where is the problem?
Everything is set up and live on the PostFinance platform.

SW: 5.7.16
PHP: 7.4
Plugin: 1.1.18

Thanks for your help