login.py fails with Plerom after secret is entered

After copying the secret over from Pleroma to command line where I started login.py I get this error:
Traceback (most recent call last):

  File "/home/utzer/.local/lib/python3.10/site-packages/mastodon/Mastodon.py", line 525, in log_in
    response = self.__api_request('POST', '/oauth/token', params, do_ratelimiting=False)
  File "/home/utzer/.local/lib/python3.10/site-packages/mastodon/Mastodon.py", line 3425, in __api_request
    raise ex_type(
mastodon.Mastodon.MastodonAPIError: ('Mastodon API returned error', 400, 'Bad Request', 'Invalid credentials')

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/utzer/ocrbot/login.py", line 66, in <module>
    cfg['secret'] = client.log_in(code=input("Secret: "), scopes=scopes)
  File "/home/utzer/.local/lib/python3.10/site-packages/mastodon/Mastodon.py", line 533, in log_in
    raise MastodonIllegalArgumentError('Invalid access token or redirect_uris: %s' % e)
mastodon.Mastodon.MastodonIllegalArgumentError: Invalid access token or redirect_uris: ('Mastodon API returned error', 400, 'Bad Request', 'Invalid credentials')

Wondering if there is any tip why the connection fails.

Start at login.py line 66 and compare the arguments passed to the Mastodon client’s log_in call with the Mastodon.py traceback. Reproduce the login flow using the copied secret, then determine why the API reports invalid credentials or redirect_uris. Done means the cause and required configuration are documented, or login succeeds.