I am trying to complete the Challenge listed for the Trailhead "Learn CRM Essentials > Data Quality > Assessing the Quality of Data". As part of this Challenge, I am expected to 'Install the Data.com Assessment App into your Developer Edition'.

1. On clicking the 'Data.com Assessment App' link provided, a new browser window opens to https://appexchange.salesforce.com/listingDetail?listingId=a0N30000000puBxEAI.
2. I click 'Get it now'.
3. I then click on 'Log in to the AppExchange (use your Salesforce credentials)'.
4. And then I get this error:

"This site can’t be reached
na45.salesforce.com’s server DNS address could not be found.
DNS_PROBE_FINISHED_NXDOMAIN"

I am unable to complete this trailhead unit as I am unable to proceed with the Installation. I am logged in to my Developer Edition where I am reviewing the trailhead.

Any help to resolve this error would be appreciated. Thanks.