Cannot download purchased Apps on iPhone to iTunes in MacBook

Just to be sure, you do realize that having them on iTunes on your Mac's hard drive doesn't serve any purpose, correct? This is probably just a holdover from past times when you couldn't download an app an infinute number of times after purchase.

They will always be in your purchased list, and you can always re-download them from there—provided you continue to use the same Apple ID.

For what it's worth, I've been getting that same pop-up you're getting ever since two days ago, the day Apple released iOS 9.2 and OS X 10.11.2 and other OS updates for their other devices. This happened to me even before I updated my OS X version. I'm theorizing they accidentally messed something up while they were making the software updates live.


Incidentally, I notice you're photographing your MacBook Pro's screen in order to take "screenshots" to share with us. Here's how you can do this without involving a standalone camera:

How to take a screenshot on your Mac - https://support.apple.com/en-us/HT201361

 

I just learned that a lot of other people with a variety of setups have been experiencing this same issue in recent days, including people using Windows.

I wouldn't worry about it too much.

 

May I ask why you want to keep a copy of the apps on the laptop?

If you ever needed to re-download any of your current apps, you can go back to the Purchased list and download it again—free of cost.

For example: Sometimes an app is temporarily reduced from its price to "FREE"—it may be an app that I don't have a need for at that moment. But I will Get the app just so that it's on my purchased list, and immediately delete it. Then I can get it again for free if I ever need to in the future—even after the temporary "FREE" cost has been raised back to normal price.

Also: I can tell you that my apps are downloading to my app library (iMac hard drive) despite the error message. I just tried it. I get the error, but the app successfully downloads. They are probably downloading ofr you as well. On your iTunes, go to My Apps and see if your apps are there, despite the error message.

 

Excellent. And here's how to check to see if your recent App downloads are indeed on your hard drive. On iTunes, find the "…". Then, find "My Apps" near the top center of that window. Below that, you will see all apps currently on your iTunes library (see below).

Here are mine (including an app downloaded today, despite the iTunes error message)… and this is only a partial list because every once in a while, I come to this very screen to delete the apps. Right now, they are taking up ~ 3.25 GB on my hard drive. It isn't much at all, but hey, I'd rather have it available to me than wasted on App files that serve no purpose.

 

Yes, definitely. You said it was a new MBP, so there should be no concerns about the its ability to handle the update. Aside from new features, updating to the latest version of OS X ensures that you have the newest security patches in place, which is always a good thing.