Marketing channel populated incorrectly

We don't see your direct rule but I take it, it is below this one looking at your screenshot. Are you looking at a date range that is post the change/creation of the rule?

Have you ensured you've typed in "utm_medium" rather than "utm_medium=" ?

As I can see in the workspace you are using "Visit" metric in Marketing channel report.If we are looking into a marketing channel report in Adobe Analytics, the Adobe recommends using only the "Marketing channels instances" metric.

This metric measures the number of times a marketing channel was defined in an image request, including standard page views and custom link calls. Does not include persisted values.

https://docs.adobe.com/content/help/en/analytics/components/marketing-channels/analyze-mc.html

Instances show the total number of times that a user clicked to your website and the Marketing Channel changed. Similar to its use in other analytic tools, the Marketing Channel persists beyond the initial click-through until the user clicks through from another campaign or referring domain. Visits here means the total number of visits where the most recent Marketing Channel was, such as email. Therefore, Marketing Channel Instances here gives the total number of clicks from email.