not_supported_on_mt4

MetaTrader 4 doesn't support this.

HTTP 400, 501. Nothing reached the broker.

Likely cause: Market depth, tick history, stop-limit orders, OrderCheck and other MT5-only features.

What to do: Use an MT5 account for this feature. Nothing was sent.

Retry: No. The same request gets the same answer; change something first.

Listed under Market data and platform support in Errors. Send the error’s requestId to support and we can find the request.