The fact that his older brother Henry was governor of Upper Silesia, may have played a rôle in his election.

He nevertheless got into a difficult position when he tried to take the interests of the Bohemian King into consideration during his negotiations with the Vatican and the council of Wrocław.

After lengthy negotiations, Pope Pius II intervened via Jošt, who was his representative Silesia.

This sermon angered the citizens of Prague and he had to seek refuge in the King's Hory castle.

His relationship with the King worsened in 1462, bowever, he was still able to mediate between the Roman Curia and the discontented utraquist nobility, who were more and more turning away from Rome.

In an attempt to prevent renewed fighting, Jošt tried to convert King George back to Catholicism and he also tried to win Queen Joanna for his position.