The error suggest that the system did not recognize the java version used. But since the current version is 1.7.0_60 it is strange that this error was generated. May be somebody from Mendix could explain this one. Have not played with the sandbox much. You could raise a support ticket for this one.
I see this post is two years old however it has not been closed.
Please make sure that the node you are deploying is a licensed node and that you have the correct node security setting permissions. Also an attempt to deploy to another node could rule this and other troubleshooting thoughts out of the question. Please try this as well.
If you have not done so already please submit a support ticket and we will look at the runtime connections, the specific cloud node connection, etc., appnode-bis-tr10026.
Keep note there is a similar ticket, so other developers may have experienced the same XMPP connection issue.