Unknown Error Occurred when attempting to download Custom Content on my Sims 3 Game!!

I understand.  It sounds like something you already have then corrupted your launcher.  If nothing new you're trying to install is working, then it must be one of your older CC items.  Do you save a backup copy of the CC you install?

No I don't, why should I?

Yes.  In case you have to get rid of it and reinstall it.  Do you clean out your DCBackup folder?  Items you have downloaded and installed will be there if you never clean out that folder (which you should do regularly). 

Ok just cleaned out my DCBackup folder, now what?

Can you un-do the cleaning?  

Sorry I wasn't clear enough....you should be cleaning out your DCBackup folder BUT IN THIS CASE, it's a good thing you don't; those downloads could be helpful. 

If you can make a folder on your desktop and put all the files that were in the DCBackup into that new folder.

ok done

Sorry but I have go deal with some RL stuff for a while.  I'm not sure what I can do to explain how to fix this problem other than deleting your CC altogether which I know you don't want to do.  Since none of things I suggested/ had you try are permanent you're basically in the same spot you started.  Maybe try following this Mac troubleshooting guide: http://forum.thesims3.com/jforum/posts/list/658546.page.  You might find it's not the CC afterall but another file in your game folder. 

So sorry...but maybe someone else has a suggestion about how to fix this.  Good Luck. 

My sim games does it also. I have no mods, but the thing is that I am downloading stuff from the Sims 3 Store. When I click download it pops up then says "Unknown Error Occurred" I think I know how it happened (at least mine) it said my World Adventures needed an update, so then I clicked yes then when it was downloading it wasn't responding so I quit it. Nothing happened it didnt ask for another update, but it wouldnt work!! I tried to find a way to fix it. NOTHING WORKS! ☹️((( I have all the expansions so its annoying ☹️((

@RozyGurl

Can you try downloading and installing the super patch? That should hopefully fix the problem you have. Click the manual patch link in my signature to be taken to the downloads page. You could also delete the ContentPatch folder from Documents > Electronic Arts > The Sims 3 and that will force the Launcher to prompt you to download and install the Store patches again.