I did follow the steps outlined in multiple posts with solutions.
Steps Taken to Resolve Issue
Clearly, I'm missing something obvious here. Please advise.
If issue still exists, follow below steps. (That resolved the issue for me)
1. GitHub Learning installation, Switch from All to selected (select markdown-portfolio)
2. GitHug Pages, Switch source to master-branch
3. Go back to course progress url [ https://lab.github.com/githubtraining/communicating-using-markdown ]
4. try resume / go back to the step