From your description, I believe you have a defective TV. Unfortunately, it happens. I had a similar issue with an Insignia Roku TV. Mine was stuck in a continual reboot after the first software update. I returned the TV to Best Buy and took home an identical replacement. It's been working fine for about 5 years now. Don't let one defective item make you feel the product is no good.
I know nothing about Hisense, other than I know they are a budget line of products. Roku doesn't manufacture the TVs, so you need to get it replaced under the Hisense warranty. Perhaps the store you bought it from will let you replace it. All depends on exactly how long you've had it and what their return policy is.
Dan
Roku Community Streaming Expert
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