must be list type

app.py

@@ -18,8 +18,8 @@ def filter_map(uhi, longitude, latitude):
 
     # Create the plot
     fig = go.Figure(go.Scattermapbox(
-        lat=latitude,
-        lon=longitude,
+        lat=[latitude],
+        lon=[longitude],
         mode='markers',
         marker=go.scattermapbox.Marker(
             size=6