not_supported_on_mt5

MetaTrader 5 can't do this.

HTTP 400, 501. Nothing reached the broker.

Likely cause: An MT4-only feature asked of an MT5 account.

What to do: Use the MT5 equivalent. 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.