CoursePress Pro unable to install


I've tried to upload the coursepress to my website but it gives me the following error:

Installing Plugin from uploaded file:
Unpacking the package…

The package could not be installed. PCLZIP_ERR_BAD_FORMAT (-10) : Unable to find End of Central Dir Record signature

I've tried unzipping it and with Peazip but the program tells me that the archive isn't readable. I get an option to give in Password and keyfile??

Downloading was already difficult. From the Coursepress pro page I've pressed install and then the option to download. That download went wrong 3 times. After only one Mb it stopped. After that I've tried the download link on the Coursepress Pro page, next to the install link, That link did work and I could download the file.

I will try to download the file with an other browser to see what happends.