ERROR: invalid GeoJson representation
From the docs on ST_GeomFromGeoJSON


  ST_GeomFromGeoJSON works only for JSON Geometry fragments. It throws an error if you try to use it on a whole JSON document.


This means you'll want to cut out just the value from the geometry in your GeoJSON document,

SELECT ST_AsText(geom)
FROM ST_GeomFromGeoJSON($${                                                                                                                          
  "type": "Point",                                                                                                                                   
  "coordinates": [125.6, 10.1]                                                                                                                       
}$$) AS geom;

     st_astext     
-------------------
 POINT(125.6 10.1)


ℹ ST_GeomFromGeoJSON is the inverse of  ST_AsGeoJSON (which only produces the geometry section of GeoJSON document.)