The is_writable function probably not work for default session path due to the permission
set on hosting server. However, session path is working fine for a folder in my account.
Thus, in lib/OX/Admin/UI/SessionStorage.php script I've defined session path as the folder
in my account. The problem is here that we have to know absolute path in hosting server to
the folder as /home/...../account_folder/session_folder.
I was told that this will not work if the script is loaded to root.
After this change installation goes smootly!
Please, consider this and make changes to the script which will be a complete solution for this problem!
Thank you for your time and effort to help to find the solution!