Usually, rebooting the internet router and reconnecting your Fire TV Stick should fix that issue.
At times, the 2.4 GHz channel gets too crowded and clogged because of several devices at home. Alternatively, if you are using a dual-band router, try connecting to a different frequency band (2.4 GHz or 5 GHz) and check if that solves the problem. If the streaming stick works with another network, you should fix the unresponsive router. Try connecting the Fire TV Stick to another Wi-Fi network -perhaps a mobile hotspot- and check if it connects without problems. You can start by checking that your internet router is transmitting data correctly.
