If what you're trying to watch is in HD, you may need to turn off (or pause) the Video Data Saver. You can also try reducing the resolution of the stream at the source, if Sling TV allows this. A lower resolution may stream better, especially during periods of high congestion. And, unfortunately, congestion is usually highest during primetime due to a higher number of people being online. The ability to stream without buffering will be determined not only by speed, but by that congestion.
One other thing to keep in mind is that streaming is a very data intensive activity, so you should pay close attention to your data usage. Streaming can use up to 3GB or more per hour in HD. You can view your data levels with the HughesNet Usage Meter, which you can get at the HughesNet MyAccount site, or by getting the HughesNet mobile app at Google Play or the App Store. You can also see your data levels in the System Control Center, as well as the Usage page on the previously mentioned HughesNet MyAccount site.
With the mobile app you can also check your WiFi signal strength to make sure it's adequate at the location of your Firestick. On the Android version, the WiFi gauge is the middle icon after pressing the plus sign on the lower right. Also, if/when you do check the WiFi signal, make sure you're mobile device is connected to the same band (2.4GHz or 5GHz) as the Firestick, as the WiFi gauge tests the band the mobile device is currently connected to. And make sure to be holding the mobile device where the Firestick is so that it's testing the WiFi signal strength at that location.
Lastly, during your first 20 days of service your data is continually refilled. HughesNet does this as a courtesy, in order to allow new customers to update and/or upgrade their devices to current without it affecting their monthly data allotment, as those activities can use a lot of data. Once the initial 20 days has passed your data usage will start being deducted in the normal manner. So, what you see during your first twenty days of service won't be what you see after them, data usage wise.
Hope this helps.
Omg! So much to remember! I never had any of these issues with At&t Uverse!😓
Most of it you'll get used to pretty quickly, and things like checking the WiFi signal strength really only needs to be done to make sure it's not contributing to the streaming issue. It's not something you'd do on a regular basis.
You do want to get in the habit of paying attention to your data usage/levels, though. You don't have to be checking it all the time, but you do want to know where you stand, data wise, on a regular basis. I tend to check mine at least once every couple of days, but if you do lot of data hungry things, like streaming, you'd probably want to check it more often. If you run out of data you're only throttled, not cut off, but it's still better to avoid having that happen when you can, and knowing how much data you have left in the current data cycle will definitely help with that.
HughesNet, like all satellite internet, is most definitely a change from ground based service, especially when compared to services that have no data cap. It's really a service of "last resort", for when you can't get ground based service. Providing a basic internet connection with adequate speed for many things, and with the addition of being able to do a little streaming if one wants, but not a lot, as the data amounts are too small to support it. You can buy data tokens if you're throttled and need the higher speed again, or if you want to avoid throttling before it happens, but that can get expensive very quickly, so most people limit data hungry activities like streaming.
But yeah, if you're used to Uverse, having HughesNet is going to be quite a bit different.