I keep getting installation error everytime I install a pack

I had this exact same issue 3 days ago.

I tried everything that was suggested here, to no avail, but then I tried some troubleshooting on my own and now it is resolved.

My first question is are you crossing over to the EA App from Origin?

If yes, my fix will probably work for you too.

**Back up a copy of your saves to your desktop.

(You probably won't need to since we won't be touching save files but better safe than sorry)

Close the EA App completely.

Go into Programs Files or Program Files (x86) on your computer.

Find and remove the folder labelled "Origin Games", place it on your desktop.
(If you do not have the space to temporarily put that folder on your desktop, you may have to delete it - If this fix works, you'll be deleting it anyway)

**This will uninstall all of the games you currently have on the EA App.

Open the EA App and reinstall The Sims 4.

This should create a new folder on your computer, in Program Files, named "EA Games".

All of your Sims 4 content should reinstall smoothly, even the ones that keep getting stuck at the 72% installation error.

My theory is that when we were forced to uninstall Origin for the EA App that folder was left behind.
Since the folder reads "Origin" and the EA App is programmed to generate and draw from its own dedicated files folder, there is a mismatch when we try to install any new content while still using that old, obsolete folder.