Currently there is no way to identify the cause of the issue when installing apps from Atlassian Marketplace. Therefore, partners cannot provide any kind of support to their customers. The only option they have is referring to Atlassian support and waiting for a reply.
It would be very helpful, if the cause of failure was made clear when installing an app instead of receiving a generic error message which indicates a system error on Atlassian’s side.
This would greatly improve user experience on the cloud.