Happy New Year everybody
I also have this problem (only Filehippo) and after a few weeks of searching I finally found a reason for this error and a solution.
It seems Filehippo changed their SSL certificate to only allow TLS 1.2 which got me thinking: why does the download work in e.g. Firefox but not in Ketarin? I then narrowed it down to Windows/.NET and found registry setting "SchUseStrongCrypto" which forces .NET to use newer settings for connections. You need to create the following keys in your registry
After that a reboot may be necessary. If you don't know what the registry is let a professional do that for you.
I'm sure there is a Windows 7 update somewhere that (should) fix that but I could not find it.
Also after the recent catastrophic Microsoft updates and the ... Windows 10 forced updates it is not in my interest to mess up a fine running Windows 7.
Hope this solution works for you too!