Hi,
I have a problem that when I add page, then Name: I can't choose any user, I only get admin user, but can't choose Registered user, what is the problem ?

- I'm using joomla 3.6 & BS MyJspace 2.6
- I follow the reguler istall steps and everything is ok
- there is no error message.

But the problem is that I can't choose user, everytime I select any user in my user list its choose automatically Admin

When you say: " I can't choose any user, I only get admin user"
When you click on the icon to select the user, what is happening?
- no popup windows, popup with only admin user (how many other user do you have?)

What is your Browser (inluding version) & Operating System?
What is the exact Joomla version Joomla 3.6.3 form example?
For the BS MyJspace version did you get the final version or any beta version?

When I click on the icon to select the user I get the popup windows with the admin user and the other users but when I choose the username it's seems there is no choice done,

I have IE11, Firefox41, chrome54
I have windows7
Last joomla version 3.6.4
and last BS Myspace Version : 2.6.0 | 446 | 16/07/2016 and not beta version

there is some image for more explain

Thank for the clear feedback. Unfortunately, you are the first with such issue. I'm not able to reproduce it.
May be another component or plugin interfere. Did you try to deactivate extra plugins installed, to try to identify the cause?