Welcome to the forum.
You need to switch the SH into modem mode with a single PC connected by cable to port one. (Next to the incoming co-ax cable) Then power it down and reconnect your LAN cable to the router.
It is important to switch things on in the right sequence. First the SH and then wait for the lights to stabilise, then the router and again wait for it to stabilise. Then the PC and other devices should be able to connect.
This allows the router to get properly registered to the SH. After this first time the sequence shouldn't matter if the setup stays the same. I've had a power outage in the past and it just all came back on fine. I do tend to just leave the SH and router on all the time as they don't take a lot of power and the smart TV needs them anyway.
HTH
__________________
History is much like an endless waltz: The three beats of war, peace and revolution continue on forever.
However history will change with my coronation - Mariemaia Khushrenada
