The dashboard is saying I'm still on a mission I've completed already.
Dataquest has a feature which gives students the ability to see where they left off the last time they were on the site. There are two components to this feature:
A banner at the top of your dashboard:
...and an arrow indicator within the dashboard itself:
These indicators feed off of our database, which is where all student progress is stored. At times of high volume, there can be a delay in the time it takes to update the dashboard with progress you've recently made.
This would make it seem that the arrow indicator and the "Continue" button are stuck on a mission you've completed already.
Not to worry!
All you'll need to do is give the dashboard some time to catch up to the database — as you continue working on the course, these indicators should reset themselves to where they should be.