Why does my code not return any values? It works for other fields, for example TR.Price.Close

import pandas as pd
import numpy as np
import plotly.graph_objects as go
import lseg.data as ld
from plotly.offline import plot
import cufflinks as cf # Cufflinks
import configparser as cp
import time

all_data = []
for i in range(0, len(RICS), batch_size):
batch = RICS[i:i + batch_size]
data = ld.get_history(
universe=batch,
fields = "TR.F.CF",
start='2010-01-01',
end='2024-01-01',
interval='yearly'
).dropna().reset_index()

RICS is definied as all companies in the S&P500