Heinsberg was the son of John II of Loon by his first wife, Margaret of Gennep. When Prince-Bishop John of Walenrode died suddenly in 1419, Heinsberg, despite his young age, was unanimously elected as his successor within three weeks. He was ordained priest on Christmas Eve 1419, consecrated as bishop in Lent 1420, and was invested with secular power as prince-bishop, on behalf of Sigismund, Holy Roman Emperor, in Frankfurt on 21 June 1420. In 1422 he took part in the Bohemian Crusade against the Hussites. In 1424 he revised the method by which aldermen were elected, issuing regulations that remained in force until 1684.