In my case, I had some proxy defined in the settings.xml file at \netbeans\java\maven\conf like :

<proxy>
    <id>netbeans-default-proxy</id>
    <active>true</active>
    <protocol>http</protocol>
    <host>******************</host>
    <port>****</port>
</proxy>

which was causing this. Once I removed it, relaunched NetBeans and tried to do a Clean and Build of the project and it worked like a charm.