Permalink isse in WPMU main site

Om my main site in a WPMU network, I decided to change my /blog/ to /fast-track/ and have made that change in my permalinks settings for the site (Network Admin > Sites > [choose site] > Edit > Settings > Permalink Structure to /fast-track/%postname%/.

When I go to https://driverevenue.marketing/fast-track/ I see my two blog posts. The link to read more (and the title link) both point to https://driverevenue.marketing/fast-track/post-name, but that 404's. When I go to https://driverevenue.marketing/blog/post-name I can see my post in its entirety.

This is weird! Changing the permalinks should put all blog posts at /fast-track/. And yes, I Purged the Siteground cache, browser refresh, etc.

How can I fix this so that all my posts are in /fast-track/ ?

Thanks,
Larry