Hey there, let's break down why your MT5 connection is failing when you add the login parameter, and how to fix it.

The Root Cause #

When you call mt5.initialize() without any parameters, it uses the saved login credentials from your MT5 desktop terminal (the account you're already logged into there). But when you explicitly pass the login parameter, MT5 expects you to provide all required authentication details—not just the account number. Missing any of these leads to the "Invalid params" error (-2).

Step-by-Step Solutions #

1. Pass All Required Authentication Parameters

You need to include login, password, and server when calling initialize() explicitly. Here's the corrected code:

account = 53895161
password = "your_account_main_password"  # Use the main trading password, not investor password
server = "your_broker_exact_server_name"  # e.g., "MetaQuotes-Demo" or "ICMarketsSC-Live"

# Initialize with full credentials
authorized = mt5.initialize(login=account, password=password, server=server)

if authorized:
    print(f"Connected to account #{mt5.account_info().login} successfully!")
else:
    print(f"Failed to connect at account #{account}, error code: {mt5.last_error()}")

• Key Checks:
  • The server name must match exactly what's shown in your MT5 terminal (case-sensitive, no extra spaces).
  • Use your main trading password—investor passwords only allow read-only access and will fail here.

2. Alternative: Initialize First, Then Login Separately

If you prefer more flexibility, split the process: initialize the MT5 connection first, then use mt5.login() to authenticate with your account details:

# First initialize the MT5 connection
if not mt5.initialize():
    print(f"Initialization failed, error code: {mt5.last_error()}")
    quit()

# Now login to your target account
account = 53895161
password = "your_account_password"
server = "your_broker_server_name"

login_success = mt5.login(account, password, server)
if login_success:
    print(f"Logged into account #{account} successfully!")
else:
    print(f"Login failed, error code: {mt5.last_error()}")

# Don't forget to shut down the connection when done
mt5.shutdown()

3. Verify MT5 Terminal Environment

• Close any running MT5 desktop instances before executing your script—conflicts between the terminal and API can cause connection failures.
• If you have multiple MT5 installations, specify the terminal path explicitly in initialize():

  mt5.initialize(path="C:/Program Files/MetaTrader 5/terminal64.exe")
  

Why the Error Occurred #

Error code -2 (Invalid params) means the parameters you passed to initialize() are incomplete or incorrect. When you omit parameters, MT5 falls back to the terminal's saved session, but explicit login requires all three core authentication details.

内容的提问来源于stack exchange，提问作者Mohamed Sayed