Well, if YouTube is working on the TV, then it's not an issue with your HN system. It may be an issue with the Netflix app on your TV. You may want to read the manual to see if there's a troubleshooting section, or contact the manufacturer.
We had massive issues with Netflix when we 1st got sat. The first thing to rule out is WiFi vs lan connection to the TV. WiFi did not work at all, Netflix would buffer all the time. With the lab connection Netflix worked with limited buffering. Also remember Netflix needs a min of 500kbps to stream, if you run low on data you will experience lag. Another important factor is your TV’s software! Roku is not recommend for HughesNet because of the latency issue with satnet. We use our Samsung blue ray player with lan connection, since we switched we have not had to many issues. YouTube will work on Hughes great because it allows the user to select the quality, Netflix does not. So if you watch YouTube you can set the quality to 144p or 240p and you will stream just fine. As I said above Netflix needs 500k minimum to stream. I hope this helped, and good luck.