Hi Why I'm unable to add hero in my formation setting ?

Something is not right with your game from the images you have. You should be able to add Razor or The Orochi to the APC formation but also the Marksman hero is a development hero and should not show in the APC formation select screen.

Definitely restart the game (close it completely) to see if that clears it. If not then you can try uninstalling and reinstalling BUT only if you have bound your game to an external account (eg IM30) to make sure you can log in again to it.

It may be best to use the in game support option to send these details to the developers, including the images. They should be able to advise or fix the problem.