maybe it is not an array

app.py

@@ -535,7 +535,7 @@ with tab2:
             
                 st.download_button(
                     label="Export player frequency",
-                    data=convert_df(summary_df),
+                    data=convert_df_to_csv(summary_df),
                     file_name='NBA_player_frequency.csv',
                     mime='text/csv',
                 )