First of all, make sure you are updated to 2015.7, which is required for the 5D Mark IV.
Go to Help > About Adobe Photoshop Lightroom to see what version you have.
If it's anything less than 2015.7, you will have to update.
First, try Help > Updates. If that doesn't work, download the 2015.7 update from here:
After a successful update to 2015.7 you should be able to import from your camera.
First make sure you are running the newest version of LR.
Second make sure the location that is selected in the destination area of the import windows is pointing to a folder that your username has Write permissions to.
What type of computer are you using and what is the exact version of the operating system it is running?
I have updated all my apps, lightroom, PS, Brigde and Camera RAW today. I
will check-in on the permissions, but why would they have changed? I am on
a laptop PC and Windows 10.
There was an update to Win 10 a short time ago, a week or a little more, that could of changed something.