We had the Gen4 service with the Voip home phone and Verizon's Network Extender. Everything worked fine for two years. The voice of course had the typical voip delay but both the home phone and the Network Extender worked great. Then - we upgraded to the Gen5 and both voice services stopped working. The Hughesnet voip home phone connections and the cell phone connections were terrible. Conversations were broken, sounded like voices were in a barrel under water and on and on. I spent hours on the phone with Hughes and finally discontinued their voice home service. The Network Extender is also now useless. I can make cell phone calls and hear the other person clearly but they cannot hear me or if they do they say I am cutting out. I spoke with technical assistance at Verizon, they ran some diagnostics but were not able to determine any problems on their end. It is strange to me that the phones worked with the Hughes Gen4 but will not work with Gen5. Other than that the new system works fine for streaming and internet connections considering that it is sattelite which is the only thing available to us at this time.
While Gen4 and your extender may have work, it's not supported by Hughesnet and isn't supported by your cellular provider... Basically, you was lucky it worked at all on Gen4...
Quoted from https://community.hughesnet.com/t5/Tech-Support/No-cellular-WiFi-calling-service/m-p/81982#M57989
Just some helpful tips - usually cell providers will have an FAQ on their website that mentions compatiblity. Here are some helpful starting areas:
Sprint AIRWAVE booster/AP
T-Mobile 4G LTE CellSpot (minitower)
Verizon Network Extender