I'm sorry to hear that you are experiencing this issue.
I have checked the account you have used to comment on this forum and I can confirm there are no PC game registered to that account.
If you have purchased the game on PC it must be registered to another Ubisoft account.
If you are unsure what the account details could be then please contact support on one of the following channels and they can assist you further:
Support Ticket
They would need you to provide an image of the CD key for Far Cry 4 and your proof of purchase.