Automated trading permission is the switch that decides whether software attached to a chart is allowed to send orders at all. It is usually more than one switch: a terminal-wide setting, a per-program setting, and on some accounts a broker-side permission, and an order goes through only when every one of them allows it.
The behaviour when permission is off is what surprises people. The program is still loaded and still running — it reads prices, updates its own state and reaches its own conclusions — but the orders it tries to send are refused by the terminal before they ever reach the server. Nothing about the chart looks wrong, and the only record is in the platform's log. That is the usual explanation when a strategy that behaved in testing appears to have done nothing overnight, and it is why permission is worth checking as a state rather than assumed as a setting.
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Choosing a Trading Platform: MT4, MT5, cTrader and the Broker's Own
The platform decides which orders you can place, whether your stops survive a closed laptop, and how much you would have to rewrite to leave. What actually differs between the options — and the point where the platform stops mattering and the broker takes over.