The UI says "Download trends for <repository> have been disabled. To enable trends, remove nexus.assetdownloads.enabled=false from nexus.properties"
There is no such line in sonatype-work/etc/nexus.properties, nor nexus-3.15.0-01/etc/nexus-defaults.properties. If I run grep -Ri assetdownloads.enabled in sonatype-work, I only see summary.html.bytes for maven-atlassian-public and maven-central, despite the displayed same message on every repository in the UI.
This repository server is not in active use, so any 30-day trend would be relying on non-existent data. I suspect this is just an incorrect error message. I downloaded several dozen components through the Central proxy yesterday and the message still shows, so there is data.