Why Is Maven Ignoring My Local Repo?

I seem to keep running into this problem regularly for things not in
Maven Central

[ERROR] Failed to execute goal
org.apache.maven.plugins:maven-site-plugin:3.3:site (default-site) on
project csharp-windows-elevate: Execution default-site of goal
org.apache.maven.plugins:maven-site-plugin:3.3:site failed: Plugin
org.apache.maven.plugins:maven-site-plugin:3.3 or one of its
dependencies could not be resolved: Could not find artifact
net.trajano.wagon:wagon-git:jar:1.0.1-SNAPSHOT in local-nexus
(http://localhost:8081/nexus/content/groups/public) -> [Help 1]

I can see the artifact in my local repo, but maven somehow feels,
because it cannot find it in my nexus repository, then it does not exist.

The side problem is, even though nexus can see the artifact in its
index, it refuses to download it.

Why do maven and nexus work so hard at ignoring artifacts?

Cheers, Eric