Southern hemisphere latitude is negative. Melbourne is −37.8136, not 37.8136 — the positive value is a valid point in Inner Mongolia and returns a perfectly good forecast.

Azimuth is north-referenced clockwise: 0° N, 90° E, 180° S, 270° W. In Australia you want 0. Open-Meteo's own API is south-referenced — the server converts, so enter the north-referenced value here.