Someone says “restart the router”, and the easiest button to find says Reset. Stop before pressing it. Restarting normally keeps the configuration; a factory reset removes it. TP-Link makes this distinction explicitly for Deco devices, and the exact controls must still be checked for your own model.
Read the action before using it
Find the model name and its current manual. Look for the documented restart or reboot command. Do not borrow a button-hold duration from a different device: the shape of a recessed button does not tell you how it behaves. For equipment managed by your internet provider, follow that provider's instructions.
Before a restart, write down the symptom: for example, both phones connect to Wi-Fi, but ordinary pages fail on both. Choose a moment that will not cut off someone's call or an important transfer. Avoid interrupting an update already in progress.
After the documented startup process finishes, repeat the same check on the same devices. If only one application was affected before, test that application too. A glowing indicator alone does not show whether the original problem has gone away.
A reset needs a setup plan
Factory reset is a separate decision. Before considering it, know how you would rebuild the connection and recover your own access to the settings. Keep a compatible configuration backup if the model supports it, and understand its restore procedure. A file saved from another model is not automatically suitable.
If a normal restart did not help, record the result and seek the next diagnostic step from the manual or support. Repeating restarts or holding Reset for longer does not establish the cause. The useful outcome is a working connection with its settings preserved, or a clear description of what still fails.