Kindly double check if you have updated both X and Cornerstone to the most recent version and you should be able to find the Permission Manager. Please take a look at the screenshot I have previously posted.
Once you're able to find the Permission manager, you will have to enable Cornerstone to the post and products by enabling them. You can do so by clicking on the switch icon. You will know if it is enabled if it turns green and you will see the configure option.
In case the issue persists, please post a new thread with your admin details so that we can check this further.