Majority of these issues are caused by Windows not being able to download .NET Framework. In order to fix that check if you have any pending Windows updates and install them.
Temporarily disabling anti-virus software, if present (avast has the most issues with installers), and running installer as an admin might also resolve the issue.
As a last resort you can try to manually install 4.7+ .NET Framework and then run RiftCat installer. Here is a download link to .NET Framework 4.7.1 https://www.microsoft.com/en-gb/download/details.aspx?id=56116
If above solutions do not work then go to C:\Users<your_username_here>\AppData\Local\Temp and look for any files named Riftcat_<some_numbers>. Send matching files to firstname.lastname@example.org.