Router keeps disconnecting

The internet line or router can fail even while Wi-Fi remains connected.

Do not factory-reset a router speculatively or indiscriminately disable Wi-Fi security or a firewall. Get permission before changing someone else’s network.

Record the times and check whether all devices fail together.
If possible, connect a PC directly to the router with an Ethernet cable. If it also drops out, Wi-Fi alone is not the cause.
Keep the router in an open, ventilated location. Use the correct original power supply and do not use damaged cables.
Read the router event log without changing settings. Report repeated line drops and their times to your provider. Do not install firmware during an unstable power supply.

Test after each step and stop when the issue is solved. Checkmarks are not permanently saved.