r6900, amber port light stays on even with port connected to tv and working

You gave us nothing to go off.
To get a hold of support. Click on "MyNetgear" at the top.
Register an account (or login) and then the device.
From there you can start the support process. Keep in mind that its only free for the first 90 days.
There's a support site with access to manuals, firmware, install guides, etc.
Go to https://www.netgear.com/support/
Type in your model number and from there it'll take you to the above.
Its a great resource to start with.

If its an ethernet port, its implying a 10/100mbps connection and not gigabit. 

Which is pretty standard for tv's. Most tv's don't have a gigabit connection, just 10/100mbps.

they don't need faster speeds than that as even a 4k broadcast only takes 25-40mbps. 

https://kb.netgear.com/23991/What-are-the-LEDs-and-ports-on-the-front-panel-of-my-Nighthawk-router-called