Hi there and welcome.
Sorry about the delay, your question went to the wrong category.
Can you tell me please the make and model of your wifi router please?
That tells me what I need to know, thank you
First step, please remove the power from the Arris and wait 10 minutes.
While waiting, power off the Roku.
Then power on the Arris, wait for 5 minutes then power on the Roku and try to connect via a network cable.
Let me know the results please
ok, I want you please to reset the Roku
To do this
From the Roku home screen, select settings > factory reset, and follow the on-screen instructions.
Or if you can not get to the menu, from the Button Reset
Locate the reset button on the Roku 3 player. It is on the backside of the player, just below the power connector. Using the tip of a pin, like an opened paper clip, press and hold the reset button for about 15 seconds, then release the button.
Then try to connect it please