Getting KeyError: "headers" from data request

Hello! While trying to search for companies in a specific country under a specific TRBC Activity name (industry or sector basically) with the SCREEN function, I get a KeyError: 'headers' from the screen data request:

Belgium = pd.DataFrame()
for item in TRBC_Sectors:
    country = '"BE"'
    activity = item
    exp = 'SCREEN(U(IN(Equity(active,public,private,primary))), IN(TR.RegCountryCode,{}), IN(TR.TRBCActivityCode,{}), CURN=USD)'.format(country,activity)
    fields = ["TR.CommonName","TR.TRBCActivity"]
    output, err = ek.get_data(exp, fields)
    Belgium = Belgium.append(output)

while TRBC_Sectors is a list with strings for each of the TRBC Activity sectors: e.g.

['5010101010', '5010101011', '5010101012', '5010201010', '5010202010', '5010202011', '5010202012', '5010202013', '5010202014', '5010202015', '5010203010', '5010203011', '5010203012', '5010203013', '5010301010', '5010301011', '5010301012', '5010301013', '5010301014']

Error message:

---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
<ipython-input-23-8361b97df6fa> in <module>
      5     exp = 'SCREEN(U(IN(Equity(active,public,private,primary))), IN(TR.RegCountryCode,{}), IN(TR.TRBCActivityCode,{}), CURN=USD)'.format(country,activity)
      6     fields = ["TR.CommonName","TR.TRBCActivity"]
----> 7     output, err = ek.get_data(exp, fields)
      8     Belgium = Belgium.append(output)

~\AppData\Local\Continuum\anaconda3\lib\site-packages\eikon\data_grid.py in get_data(instruments, fields, parameters, field_name, raw_output, debug)
    195         return result
    196 --> 197     return get_data_frame(result, field_name)
    198     199 
~\AppData\Local\Continuum\anaconda3\lib\site-packages\eikon\data_grid.py in get_data_frame(data_dict, field_name)
    244         headers = [header.get('field', header.get('displayName')) for header in data_dict['headers'][0]]
    245     else:
--> 246         headers = [header['displayName'] for header in data_dict['headers'][0]]
    247     data = pd.np.array([[get_data_value(value) for value in row] for row in data_dict['data']])
    248     if len(data):

KeyError: 'headers'