I set up a new community in my dev edition but get the following error message when attempting to access it: 
URL No Longer Exists
You have attempted to reach a URL that no longer exists on salesforce.com.

As I set this up yesterday and activated the community today, not sure why it's giving this error message.  How do I fix it?

I'm unable to create a guest admin as part of the exercises in the Data Security module in Trailhead.  The license and related profile simply are not in dropdowns when adding new user,although the required sys admin profile actually exists in my developer edition.  How did people get around this? (PS - I'm in Data Security Module / Controlling Access to the Organization)

I'm unable to create a guest admin as part of the exercises in the Data Security module in Trailhead.  The license and related profile simply are not in dropdowns when adding new user,although the required sys admin profile actually exists in my developer edition.  How did people get around this? (PS - I'm in Data Security Module / Controlling Access to the Organization)