December 2020
This happened some time ago, and my problem actually fixed itself when the game updated. However, when I went into the game, I turned on allow cc/mods and when I tried opening the game again, I got an error.
After I tried uninstalling all mods, it wouldn't work, and repair didn't either, so I uninstalled/reinstalled. Now I get the error again that Origin was denied access to C:\Program Files(x86)\Origin Games\The Sims 4\_Installer\DLC\GP04\_Installer\installerdata.xml_DiP_STAGED
(Happening for all my dlc/packs; vampires, holiday celebration pack, realm of magic)
Sadly the game is up to date now so I can't do the original fix I did.
(Sorry if this doesn't make much sense)
December 2020
This is because of your security software blocking access to the folder. You need to give Origin access or temporarily disable antivirus while installing.
December 2020
Origin has permission on norton, but to test I tried disabling auto-protect and firewall on it yet it hasn't worked. I even tried running Origin as administrator.
December 2020