Downloading ANY Asset,Can't download assets

I'm on a MacBook Pro btw 8 gigs ram and Nvidia g force graphics card (crap) anyways, im on unity trying to download and import Post Processing Stack, and whenever I do it in Unity, I click download, it loads to 100 percent, and the button says download again. The package isn't imported or anything. I checked my finder and the package is there in my library under user > Library > Unity > Asset Store-5.x > Unity Technologies > Unity Essentials > Post Processing Stack.unitypackage. Of course, the package still isn't there in my project, so I drag it from finder to project view and it gives me an error saying that all files in that package are already imported. Whenever I go back to the asset store in unity, and click download again, nothing happens, and it gives me an error in the output saying:
"Will not download post processing stack. Download is already in progress. UnityEditor.WebJSProxyMgr:DoTasks() PLEASE HELP!!!!,I'm trying to download and import Post Processing Stack made by Unity onto my project. However, whenever I open up Unity, go into the Asset Store (in Unity) find the asset package, and click download, it loads to 100%, and then the button says Download, again. I go into Finder, see the package is there. I try to see if maybe it did download and import the package already, and it did not. I try to drag the package from finder to unity into the Project view, and it says all files in that package have already been imported, even though I know that they haven't. Please help!