I'm sorry to hear that you are experiencing issues installing Far Cry 5.
Can you please go through these PS4 troubleshooting steps then try again.
If the issue persists I would recommend trying to install it on another console if possible, this will confirm if there is an issue with the disc or not.
However if this is not possible I would advise taking the game back to your point of purchase if you have recently purchased the game and ask for a replacement.