Primero production setup issue

Hey @irlawrence thanks for your support. Can you please give me some info as why it could be using the system ruby instead of using ruby 2.4.3 railsexpress? Is it because it is not able to download it during deploy?..what wrong could I be doing because I have cleaned my target machine completely, installed ubuntu 16.04 and followed all steps as mentioned here How can I quickly set up Primero.
What could be causing this issue?
Please suggest me with some solution as I am stuck here. Thanks in advance.