After submitting to one of the journals in Elsevier recently, 
we got a response as following:  

> I think the manuscript can be improved and should be resubmitted, but the changes will probably take too long to accomplish within a "major revision" timeline.

 The editor wrote that they were only able to find one reviewer and the final decision was a "*reject*."

The reviewer had made detailed suggestions for improvement and asked for files and figs.
Within a month, we re-submitted to the same journal addressing all the revisions, mentioning these point-by-point in the communication to the Editor.

The journal sent back an automated message without any comments or reason stating it has been rejected, after a week from submission.

Does anyone have a clue on what is happening?

Is this a technical issue? In the past, Elsevier's system seems to have been hacked.