Point m2e at the Maven Settings That Contain the Proxy

In Eclipse, open Preferences → Maven → User Settings and check the displayed path. m2e uses Maven settings.xml for proxy configuration; a working Eclipse update-site request does not establish those inputs. The normal user default is ~/.m2/settings.xml, but the IDE can select another file.

Merge a proxy entry into that document's top-level proxies section:

<proxies>
  <proxy>
    <id>office</id>
    <active>true</active>
    <protocol>http</protocol>
    <host>proxy.example</host>
    <port>8080</port>
    <nonProxyHosts>localhost|127.0.0.1</nonProxyHosts>
  </proxy>
</proxies>

Replace the endpoint and intended bypasses while keeping mirrors, server accounts and other settings. For a public repository on a network that permits an independent proxy route, an unauthenticated candidate from the HTTP proxy list can supply the host and port; confirm that it permits the repository connection. Add Maven's proxy username/password fields when that intermediary requires them.

Apply the selected settings and update the affected Maven project. Compare with the successful command-line invocation's actual settings override and merged global settings. Choosing another Maven distribution is separate: it can change launches/global inputs but does not add the proxy to the correct user file.

Use the response to choose the next branch. A 407 concerns proxy login; a repository 401 concerns its own account, matched through a servers entry to repository or mirror ID. A server private-key field does not implement HTTP proxy authentication. Certificate errors are another condition. Keep environment routing in settings rather than putting it in the project POM.