Hi Basel,
Thank you for identifying this problem. A fix is in the works and we will be updating the lesson as well. In the meantime, you can get around the issue by following these steps before the steps in the Derive new locations section of the lesson.
1. In the Content pane, click on the ellipsis beside the gastransactions layer and choose Save Layer
2. Click the elipses again and click Show Item Details.
3. On the Item Details page, click Publish.
4. Return to your map. Click Add and Search for Layers. Add the new version of the Gas Transactions layer that you just published.
5. Continue on with step 1 in Derive new locations
Now that the layer is published as a hosted service, the Derive New Locations expressions should work without issue.