Purchased theme "Good-Minimal" from Themeforest that won't upload

Hi,
I just purchased a premium theme called “Good-Minimal” from theme forest, and downloaded into a zip file on my mac. When I try to install it to my WP site, it won’t upload. I’ve tried dozens of times, using different browsers, and I keep getting the same error message:

“Are you sure you want to do this? Please try again.”

Other themes are installing fine, so I’m wondering why the one premium theme that I paid money for won’t work. I haven’t heard back from theme forest yet with any help, so any advice is appreciated.