Internet hasn't worked since I got it

We got our HughesNet Satellite internet installed a week ago and it has not yet worked correctly. I've spent at least 4 hours on the phone with Tech Support and while they have been very kind, I keep being told to call back later when they can do more tests or to let the system sit to see if the setting adjustments we made on the call take hold. I let it sit for the weekend and it's still not loading webpages or videos properly. When I do a speed test, everything looks like it should be fine but I'm still experiencing long buffering times and  Amazon Prime Videos (regular streaming) won't play at all. Even when the TV is hooked up to the modem with an Ethernet Cable, videos still won't load. Please help!