Netflix

Ok, just wanted to make sure. I assume the Netflix app is also up to date.

I would also verify the network just to double check there are no other issues that could be causing this.

Use the speedtest app to see the internet connection being received

If on wifi try Apple TV on ethernet

Netflix recently changed their requirements, make sure your Apple TV is up to date.

It would mean the Apple TV operating system. Just for clarity, what version of TVOS is running on your system?