Install KNIME Extension - Error

After having KNIME plafform installed and running on a Windows environment, I was able to upload data to be analyze. However I encountered an error when going to install extensions. 

I took the following steps:

1. Open KNIME Plataform

2. Going to install Extension following video guide 

3. Under File, selecting Install KNIME Extensions

4. I get the error: Contacting Software Sites has encoutered an error. - Link to a screen shot of the error 

Will appreciate if you can advice how to overcome the error. 

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