Apm stay in same firmware after update

For some reason I decided to check my apm version.
after I checked using the cli I discovered that the firmware has never update.
I update the firmware many times but with no success.
the apm refused to update and stays in 3.2.1 version.
the weird thing in that is the mission planner looks like there is no problem with the update and tell me that the software successfully updates.

This is latest version for APM. It’s not supported anymore.

Mission Planner identifies it as an APM Flight Controller and automatically loads the last supported version as Piotr says. Buy a PIxhawk or Pixhawk variant.