day old Home Internet randomly stops

Just picked up a replacement Home Internet Gateway. After 1/2 hour, it stopped and would not restart until this morning. Today, after 2 hours use, it stopped again and needed restarting. 

Suggestions? 

Oh yeah, the T-Mobile store is a 130-mile round trip for me, so maybe someone can tell me I missed something.

I had Verizon home internet for 3 problem free years, then I moved out of their coverage area. First TMobile gateway died yesterday, now the replacement is flakey!