I am also understanding that Ren views Darth Vader as the true personality of his grandfather and that reedeemed Anakin was just a corrupted version of him. So even if a force ghost talked to him he might dismiss it as not his true character or some sort of Jedi trickery.
I like this theory, but in order to be consistent I have to ask was there anything in the film that supports it?
There was a deleted scene supposedly that said this:
From http://www.starwarsnewsnet.com/2015/12/the-deleted-scenes-of-star-wars-the-force-awakens.html
Kylo Ren and Supreme Leader Snoke had a discussion about Darth Vader. Snoke says that he viewed Vader as an exemplary individual who let sentiment get the better of him, and Kylo agrees. The conversation also reveals that Snoke was old enough to have witnessed the Clone Wars in their entirety.