This is my first time posting a new thread so please excuse me for any confusion. I got the Sims 3 starter pack & expansion pack for Christmas and I installed everything last night (with the exception of Late Night because that pack just screwed everything up). I am now trying to install custom content. I have a MacOS Sierra (Version 10.12.2). I went to Documents >> Sims 3 and created the Mod folder. Within the Mod Folder (and yes I have it typed exactly "Mods") I have the resource.cfg file (downloaded via y'all) and a folder named "Packages".
I put the tester mod in it (the "nointro.package") and have had no success. What am I doing wrong?

Does the CC have the sims3 logo for an icon? If it does it has to go to the downloads folder

I'm having the same problem but with an HP notebook, windows 10... I've fallowed directions exactly as i've read them, but the intro mod wont work and neither will anything else that gets put there. The packages themselves don't show the sims icon, but the one other mod i tried downloading (in hopes that it may work) does.
Not sure what to do at this point

windows 10....
Look in One Drive. Do you have an Electronic Arts folder in there as well?

This wouldn't apply to a Mac, though.

The one step you seem to have left out here is that you would need to delete your TS3 folder's scriptCache.pacakge file (it will regenerate) whenever adding or removing any mods. Does doing that make your test mod get recognized and work?

If that doesn't do it, I would suggest removing your TS3 folder from Documents, pull it to your Desktop for safekeeping, and let the game generate a fresh game folder on its next attempted launch. Then back out and try the Mods folder setup with the test mod again.

TS3 for Mac is a mess. I hate to say this because I love TS3 and Macs (independently of each other), but a stubborn Mods folder might only be the beginning of your worries. What kind of Mac do you have and is bootcamping Windows within your reach?