I am trying to set up a custom domain in a delevoper edition of Salesforce in conjunction with a trailhead course.  When I click the Check Availability button, I always get the same message.  I have tried many different domain names and always get the same message.  The error is as follows:

Your domain name can include up to 40 characters, numbers, and hyphens. The name can't begin or end with a hyphen.

Any suggestions?  My Domain name does not start or end with a hyphen.  See screen shot below

Trying to complete Trailhead challeng Building a Custom Record Page for Lightning Experience and getting an error that its not right.    It says I don't have the right components on the page.  I think that i do and they are all named correctly.  One possible question is it wants me to add the Feed Component to a tab.  Is that the same as Chatter Feed?  If not, then Feed does not show up as an option.  Suggestions?  It is looking for the following ( I have completed all of these steps.  error message is 'Lightning Page named 'New Account Page' does not appear to have the correct components on it'):
1. The new record page must use the 'Header and Two Columns' template, be called 'New Account Page', and be assigned to the Account object.
2. The page must have the Highlights Panel and Twitter components, and a Tabs component with these tabs containing these components:
         - Activity Tab contains the Activities Component
         - Collaborate Tab contains the Feed Component
         - Related Tab contains the Related Lists Component
         - Details Tab contains the Record Detail Component
3. The page must be activated.

I am trying to set up a custom domain in a delevoper edition of Salesforce in conjunction with a trailhead course.  When I click the Check Availability button, I always get the same message.  I have tried many different domain names and always get the same message.  The error is as follows:

Your domain name can include up to 40 characters, numbers, and hyphens. The name can't begin or end with a hyphen.

Any suggestions?  My Domain name does not start or end with a hyphen.  See screen shot below

Trying to complete Trailhead challeng Building a Custom Record Page for Lightning Experience and getting an error that its not right.    It says I don't have the right components on the page.  I think that i do and they are all named correctly.  One possible question is it wants me to add the Feed Component to a tab.  Is that the same as Chatter Feed?  If not, then Feed does not show up as an option.  Suggestions?  It is looking for the following ( I have completed all of these steps.  error message is 'Lightning Page named 'New Account Page' does not appear to have the correct components on it'):
1. The new record page must use the 'Header and Two Columns' template, be called 'New Account Page', and be assigned to the Account object.
2. The page must have the Highlights Panel and Twitter components, and a Tabs component with these tabs containing these components:
         - Activity Tab contains the Activities Component
         - Collaborate Tab contains the Feed Component
         - Related Tab contains the Related Lists Component
         - Details Tab contains the Record Detail Component
3. The page must be activated.