Why the Missing 64-bit support happened when upload to the iTunes connect?

Question

I try to upload the file via Application Loader. But I got the mail from iTunes store.

Missing 64-bit support - Beginning on February 1, 2015 new iO

Answer 1

Most commonly happens when I archive while a device is connected (as it affect the architecture).

(As mentioned in a comment by Martin to Shashi3456643's answer)