I'm sorry I didn't take a look at the exact error message in your initial post.
Here is a part of the Installation Troubleshooting article in the documentation
Error message "This installation package could not be opened. Contact the Application vendor to verify that this is a valid windows installer package"
There are two possible reasons for this error to happen:
- The installation file got corrupt during the download
- The installation file was downloaded to a compressed folder and/or the temp folder on the machine is compressed
Log in to your Telerik account and download the RadControls installer again. An md5 hash sum calculator can be used to verify the new download is not corrupt (the fciv utility is such a tool). Download the installation file to a non-compressed drive.
Can you please, follow the steps above?
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