Disclaimer: I'm just a forum member. The official support is AndrewT or Icratox for instance. So take my advice with a grain of salt or wait until someone official responds.
Steam or GG ?
Did the game run fine before ?
What Patch are you running ? (visible in the main menu, only right after start up.)
Have you patched from 1.111 to 2.0 or from a far earlier patch ? If so, maybe your portrait DLC haven't been updated correctly.
You could try to delete the
C:\Users\<Name>\Documents\Paradox Interactive\Crusader Kings II (where <name> is your Windows user name) folder.
Move your save files first. No need to delete them as well.
The directory wil be recreated after starting up the game again.
If you are unsure about what i say or what you should do, just respond as far as you can and wait until one of the officials show up.