I'm trying complete the Lightning Experience Rollout Specialist challenge #1, but i cant use Optimizer tool.

If i go to http://optimizer.salesforce.com/, i receive this message:
Offline for maintenance
This app is undergoing maintenance right now.
Please check back later.
On Trailhead playground, Setup>>Monitor>>Optimizer, same message:

I'm trying complete the Lightning Experience Rollout Specialist challenge #1, but i cant use Optimizer tool.

If i go to http://optimizer.salesforce.com/, i receive this message:
Offline for maintenance
This app is undergoing maintenance right now.
Please check back later.
On Trailhead playground, Setup>>Monitor>>Optimizer, same message:

I found this error while finishing this challenge in" Implement Block Pricing" error is "The first Block Price for the Mobile Control Center App is not configured correctly. Check the Lower Bound, Upper Bound, and Price".can anyone help rectify this errors.

Trying to complete this Challenge, but keep getting the following error despite many variations on trying to load the file.  I think I've also completed the rest of the challenge, but am unable to even check since I can't seem to get past this first "easy" part.  Thoughts?
 

• {!c.Name}

Here are the directions:

Use Bootstrap to create a simple mobile friendly list of existing contact names and display the page within Salesforce1 mobile. The Visualforce page:Must be named 'MobileContactList'.
Must reference the minified Bootstrap JavaScript and CSS files from MaxCDN (see more here). Do NOT use Static Resources to reference these files.
Must use the Bootstrap List Group component (defined here).
Must use the Contact standard list controller with a recordSetVar of 'contacts'. The list of contacts must be iterated through using an apex:repeat component that's bound to a var named 'c'.
Must display the name of the contacts.
Must be made available for the Salesforce1 mobile app and added to a tab named 'MobileContacts'. The tab should be added to the Salesforce1 navigation menu.