Can't install themes from dashboard

Hi there,

I just bought a new premium theme and tried to upload it through my dashboard, but for some reason it just won’t install. Every time I try I get the same message: “Install package not available.” I know I am uploading the correct .zip file… I even try to upload another premium theme that I uploaded and installed without issues on another website, and I get the same message. What could be wrong?

Havard