"fields", приходит только последнее поле указанное в кортеже.array = {'group_id': 98446009, "sort": "id_desc", "offset":i,"fields" : ('online', "sex"),
'access_token': good_token, 'v': '5.103'}
members1 = requests.post('https://api.vk.com/method/groups.getMembers', data=array,
headers=headers).json()params = {'group_id': 98446009, "sort": "id_desc", "offset": i, "fields": "online, sex", 'access_token': good_token, 'v': '5.103'}
members = requests.post('https://api.vk.com/method/groups.getMembers', data=params, headers=headers)
print(members.json())fields должны быть перечислены через запятую