Market data and order routing are two different systems, and they fail separately

Something professional setups treat as obvious and retail material rarely says out loud: your quote feed and your order path are separate systems. Different servers, different connections, different failure modes. This matters because the symptoms look identical from where you sit. Nothing is happening. But "I can't see the market" and "I can't reach the exchange" require opposite responses — the first means stop trading because you're blind, the second means your existing orders may or may not still be live and you need to find out before you do anything else. Worth knowing, per broker, which of your two channels just went quiet. If your app shows one status light for both, it's showing you less than you need. The practical version: when things go wrong, the first question isn't "is it broken" but "which half."