[Python] IBKR OAuth 1.0a - /request_token returns 401: invalid consumer

I'm trying to integrate Interactive Brokers (IBKR) OAuth 1.0a into my application. Currently, I'm stuck at the request token step (/oauth/request_token), where I receive a 401 error: invalid consumer.

Request Details:

• OAuth Consumer Key: TESTCONS (for testing)
• Signature Method: RSA-SHA256
• Callback URL: oob (out-of-band)
• Nonce and Timestamp: Generated dynamically
• Private Key: Loaded directly in the script

Code:

import requests
import time
import uuid
import urllib.parse
from requests_oauthlib import OAuth1

# API endpoint
url = "https://api.ibkr.com/v1/api/oauth/request_token"

# OAuth parameters
oauth_params = {
"oauth_consumer_key": "TESTCONS",
"oauth_signature_method": "RSA-SHA256",
"oauth_timestamp": str(int(time.time())),
"oauth_nonce": uuid.uuid4().hex,
"oauth_callback": "oob"
}

# Load RSA private key (masked)
private_key = """-----BEGIN PRIVATE KEY-----
MIIEvQIBADANBgkqhkiG9w0BAQEFAASCBK... (masked)
-----END PRIVATE KEY-----"""

# Create OAuth1 object
auth = OAuth1(
client_key=oauth_params["oauth_consumer_key"],
signature_method=oauth_params["oauth_signature_method"],
rsa_key=private_key,
nonce=oauth_params["oauth_nonce"],
timestamp=oauth_params["oauth_timestamp"],
callback_uri=oauth_params["oauth_callback"]
)

# Make the request
response = requests.post(url, auth=auth)

# Check response
if response.status_code == 200:
credentials = urllib.parse.parse_qs(response.text)
print(f"Request Token: {credentials.get('oauth_token')[0]}")
print(f"Request Token Secret: {credentials.get('oauth_token_secret')[0]}")
else:
print(f"Error: {response.status_code}")
print(response.text)


Error Response

{"error":"id: 92177, error: invalid consumer","statusCode":401}```

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