Specified API key is invalid error

I was trying to execute the following the below codes (copied from the basic tutorial) but kept getting errors 'ServerException: SimFin server error: The specified api key is invalid.' I have installed the simfin as well as have a valid key. What could be the cause of this? Does it not work with python 3.7 or above? Thanks!

import simfin as sf

# Set your SimFin+ API-key for downloading data.
sf.set_api_key('my_API_key')

# Set the local directory where data-files are stored.
# The directory will be created if it does not already exist.
sf.set_data_dir('~/simfin_data/')

# Download the data from the SimFin server and load into a Pandas DataFrame.
df = sf.load_income(variant='annual', market='us')

# Print the first rows of the data.
print(df.head())

This is the full error...
Dataset "us-income-ttm" not on disk.
---------------------------------------------------------------------------
ServerException Traceback (most recent call last)
in

~\Anaconda3\lib\site-packages\simfin\load.py in load(dataset, variant, market, parse_dates, index, refresh_days)
130
131 # Download file if it does not exist on local disk, or if it is too old.
--> 132 _maybe_download_dataset(**dataset_args, refresh_days=refresh_days)
133
134 # Lambda function for converting strings to dates. Format: YYYY-MM-DD

~\Anaconda3\lib\site-packages\simfin\download.py in _maybe_download_dataset(refresh_days, **kwargs)
289 url = _url_dataset(**kwargs)
290
--> 291 return _maybe_download(name=dataset_name, path=path,
292 download_path=download_path,
293 url=url, refresh_days=refresh_days)

~\Anaconda3\lib\site-packages\simfin\download.py in _maybe_download(name, url, path, download_path, refresh_days)
237 # Download the file from the SimFin server.
238 # This is assumed to succeed unless an exception is raised.
--> 239 _download(url=url, download_path=download_path)
240
241 if download_path.endswith('zip'):

~\Anaconda3\lib\site-packages\simfin\download.py in _download(url, download_path)
165
166 # Raise exception with the error message from the server.
--> 167 raise ServerException(error)
168
169 # Or if another error occurred.

ServerException: SimFin server error: The specified api key is invalid.