Uploading firmware to Pixhawk 1

I have a 3DR pixhawk that I haven’t used for awhile and wanted to load arduplane on it. With Mission Planner 1.3.72 build 1.3.7463.24854 I kept getting no response from board (System.Exception: timeout waiting for responce) I tried with 2 computers same error and than I got out a old laptop with version 1.362 build 6917.15581 and it installed firmware first time.
Is that just a bug or is Mission Planner moving away from supporting older hardware?

Please retry latest beta mp

Hello im having same/simulare problem with same misson planer, alsow it dont let me update to beta -
i have tested it with 2 difrent computer and difrent Pixhawks all give me the same Error no respons from board or time out error . Any sugestions.

Please try beta again