Problem with CMD_API_SHOW_ALL_USERS empty array

Hi,
I'm learning DA API's for my project and i'm testing the simplies way to coect with my DA account (admin of course) for now.
CMD_API_SHOW_USER_USAGE?user=user_name work fine, I can see nice array as a result.

But second day i'm fighting with the CMD_API_SHOW_ALL_USERS command or CMD_API_SHOW_USERS or CMD_API_SHOW_USERS=?reseller=reseller_name
I always get empty array as result: Array ( )
I tried to coect with and without SSL, always same result empty array.

I use simpliest code:

I tried coecting with httpsocket.php and coection was ok, but still same empty array.
Of course on the server there are ~300 hosting accounts. Hosting providers tells me that tehy dont block any of apis commands and my account have all rights to api.
I tried to print_r result before decoding and it was empty too for this commands. For command CMD_API_SHOW_USER_USAGE?user=user_name it was ok.

Very strange thing, could some one can help me?