Windows 7 64-bit: Could not find a valid gem 'compass' (>= 0), here is why: Unable to download data from https://rubygems.org/

Try upgrading your SSL certificates.

1. Download http://curl.haxx.se/ca/cacert.pem

2. Save this file anywhere you want, such as:

   C:\cacert.pem

3. On the command line, tell Ruby where to find the cert file, such as:

   set SSL_CERT_FILE=C:\cacert.pem

4. Try again.

   gem install compass

5. If it works, you can make the cert file permanent by adding it in your control panel.

Credit and more info: https://gist.github.com/fnichol/867550

Just an additional option for lazy people who don't want to deal with the SSL certificates, you can just uninstall and re-install the latest ruby environment. I used to have 1.8 something and reinstalling to 2.2.1 did the trick.

link for windows

If there are still guys like me that can't find solution in any of the comments before mine, here's how I found my working way:

I went to rubygems.org/pages/download and downloaded zipped file. Then I unpacked it somewhere on my C: partition and opened it once I unpacked it. Find a file "setup.rb" and double click on it, it will install something, I don't remember. I guess ruby gems. Then close everything, go again and open cmd on windows and try typing "gem install sass". It worked for me. Sass installed. :)

Hope I will help someone, because I lost my mind looking for solution to this problem whole day today. :)