Is Jason not showing up in your character select screen yet? Well try this fix for PS4 and you will be able to play as Jason.
- Go to the store and install Jason DLC
- Choose a single one player fight and choose any characters
- While the match is loading, press the PS button and go to Netflix and open the app
- After a few seconds, go back to the Mortal Kombat X game then press start and choose player select
- Jason will be added to the select screen
This is the only way to play as Jason until the PS4 version is fixed. Hope this helps!