I find the solution, that’s a WordPress 4 year’s bug. Here is the Summary from DrewAPicture
changed from manually created user roles not showing in author dropdown irregardless of assigned capabilities to Manually created user roles not showing in author dropdown regardless of assigned capabilities
Please see ticket 16841 for more details.
The only simple solution I find is to change the author with a custom role to the normal Author role. Then attribute the custom post to this author and change back the same author with the custom role.