Image uploading button is not appearing for authenticated users,only for admin
I just had the same issue and this is what I found to fix it. 

If you have IMCE to control your file browser you must create a profile for each user role. For example, the website administrator (owner of the website) will have access to the file browser no matter what, but if you have another authenticated user with the administrator role, they will not have access to the file browser unless you add a profile to the administrator role. So to do this go to 'admin/config/media/imce' or if you would prefer the interface way, log in as administrator and click on "Configuration" -> "Media" -> "IMCE". 

Create a new profile by clicking on "Add New Profile" link and configure the profile to your needs. Save the profile. 

Then next to the administrator role (or whatever role you need this for), select that profile you just created and click save.

Now test on a sample administrator (or whatever role you configured) account.