S3 buckets in the eu-central-1 (Frankfurt) region are not not working with trovebox.
I think this is because eu-central-1 only accepts Sigv4. I can confirm that S3 buckets in eu-west-1 (Ireland) are working though. I am not sure when Sigv4 is being rolled out to other regions but it is a potential problem that needs to be solved at some stage. For more details see: boto/boto#2741

[Thu May 28 12:09:29.443753 2015] [:error] [pid 837] [client x.x.x.x:58533] PHP Notice: curl_setopt(): CURLOPT_SSL_VERIFYHOST no longer accepts the value 1, value 2 will be used instead in /var/www/openphoto/src/libraries/external/aws/lib/requestcore/requestcore.class.php on line 613, referer: http://ec2-x-x-x-x.eu-central-1.compute.amazonaws.com/setup/3 [Thu May 28 12:09:29.491270 2015] [:error] [pid 837] [client x.x.x.x:58533] {severity:warn, description:"Uncaught exception (/var/www/openphoto/src/libraries/external/aws/lib/requestcore/requestcore.class.php:797): cURL resource: Resource id #24; cURL error: SSL: no alternative certificate subject name matches target host name 'trovebox.test.s3.amazonaws.com' (51)", additional:}, referer: http://ec2-x-x-x-x.eu-central-1.compute.amazonaws.com/setup/3