Primary Reference is the Bible version that you chose to hear as the default reference as you translate and evaluate you work in Render.
To select a Bible version as the primary reference for translation using Render, you need to access the configure role. From there, you need to click on the 'USERS' icon, shown below:
Now you will come to the 'USERS' page, listing all the available Render users belonging to the project. You will have to -
1. Select a user role.
2. Click the 'EDIT' button.
Notice that the selected user does not have a Primary Reference selected, marked in the red box.
This will now bring you to the 'Edit User' page. Towards the bottom:
1. Click the 'Primary Reference' drop down menu.
2. Select your preferred Bible version as the Primary Reference.
3. Click the yellow 'Submit' button.
You will have to do this for each user role you find on the 'USERS' page. After you have done this for each and every user on the project, go back to home page and do a web sync. It will ensure that all users will now have a Primary Reference after they themselves do a web sync.