Support intro
Sorry to hear you’re facing problems 
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In order to help you as quickly as possible, before clicking Create Topic please provide as much of the below as you can. Feel free to use a pastebin service for logs, otherwise either indent short log examples with four spaces:
example
Or for longer, use three backticks above and below the code snippet:
longer
example
here
Some or all of the below information will be requested if it isn’t supplied; for fastest response please provide as much as you can 
Nextcloud version (eg, 12.0.2): 13.0.5
Operating system and version (eg, Ubuntu 17.04): CentOS 6
Apache or nginx version (eg, Apache 2.4.25):
PHP version (eg, 7.1): PHP 7.1.20
The issue you are facing:
I can not add a S3 Storage Bucket which is not from Amazon S3 Service, Im using gridscale S3 Storage, but it doesnt accept it, even the support could not identify the problem, due its working on their side.
I hope you can help. Thanks
The output of your Nextcloud log in Admin > Logging:
Error files_external Exception: The configured bucket name is invalid: S3StorageTest
/var/www/virtual/petrk/nextcloud.xxxx.de/apps/files_external/lib/Lib/Storage/AmazonS3.php - line 577: OCA\Files_External\Lib\Storage\AmazonS3->getConnection()
/var/www/virtual/petrk/nextcloud.xxxx.de/apps/files_external/lib/config.php - line 234: OCA\Files_External\Lib\Storage\AmazonS3->test(false, true)
/var/www/virtual/petrk/nextcloud.xxx.de/apps/files_external/lib/Controller/StoragesController.php - line 256: OC_Mount_Config getBackendStatus('\\OCA\\Files_Exte...', Array, false, true)
/var/www/virtual/petrk/nextcloud.xxx.de/apps/files_external/lib/Controller/StoragesController.php - line 305: OCA\Files_External\Controller\StoragesController->updateStorageStatus(Object(OCA\Files_External\Lib\StorageConfig), true)
[internal function] OCA\Files_External\Controller\StoragesController->show(1, true)
/var/www/virtual/petrk/nextcloud.xxx.de/lib/private/AppFramework/Http/Dispatcher.php - line 161: call_user_func_array(Array, Array)
/var/www/virtual/petrk/nextcloud.xxxx.de/lib/private/AppFramework/Http/Dispatcher.php - line 91: OC\AppFramework\Http\Dispatcher->executeController(Object(OCA\Files_External\Controller\GlobalStoragesController), 'show')
/var/www/virtual/petrk/nextcloud.xxx.de/lib/private/AppFramework/App.php - line 115: OC\AppFramework\Http\Dispatcher->dispatch(Object(OCA\Files_External\Controller\GlobalStoragesController), 'show')
/var/www/virtual/petrk/nextcloud.xxx.de/lib/private/AppFramework/Routing/RouteActionHandler.php - line 47: OC\AppFramework\App main('OCA\\Files_Exter...', 'show', Object(OC\AppFramework\DependencyInjection\DIContainer), Array)
[internal function] OC\AppFramework\Routing\RouteActionHandler->__invoke(Array)
/var/www/virtual/petrk/nextcloud.xxx.de/lib/private/Route/Router.php - line 297: call_user_func(Object(OC\AppFramework\Routing\RouteActionHandler), Array)
/var/www/virtual/petrk/nextcloud.xxxx.de/lib/base.php - line 999: OC\Route\Router->match('/apps/files_ext...')
/var/www/virtual/petrk/nextcloud.xxxx.de/index.php - line 42: OC handleRequest()
{main}```
The output of your config.php file in `/path/to/nextcloud` (make sure you remove any identifiable information!):
PASTE HERE
The output of your Apache/nginx/system log in `/var/log/____`:
[Tue Aug 07 12:34:54 2018] [crit] [client 2001:16b8:6690:6600:69fd:4e38:e3e1:da2f] (13)Permission denied: /var/www/virtual/petrk/nextcloud.xxxxxxx.de/data/.htaccess pcfg_openfile: unable to check htaccess file, ensure it is readable