Eisner attended primary (Volksschule) and secondary (Hauptschule) schools, and completed his education in Fachhochschule.
After the failed uprising against the Austrian state, Eisner tried to convince his former Heimatschutz members and the NSDAP group they had built with others to follow the Vaterländische Front.
In June 1936 Eisner became the illegal Kreisleiter (Nazi Party county leader) of Voitsberg.
He once stated that Hubert Eisner was still candidate for Kreisleiter, but he could not achieve this function against internal opposition.
Beginning in August 1939, Eisner was installed as Kreiswirtschaftsberater (county economic minister) and in April 1940 he finally took over Weissensteiner's agenda and became deputy Kreisleiter.
In November 1941, after Weissensteiner was called to army service, Eisner finally took over the position of Kreisleiter in the county of Voitsberg.