If you have a mobile hotspot available to you, you can try connecting your TV to it to see if you can get through setup.
If you can successfully get through setup, navigate to Settings..Systems..About and see if you have a MAC address showing. If these are all zeros, then the NIC card (wireless network chip) has an issue (especially if you are seeing no networks at all, not even neighbors. You can sometimes fix this with a soldering iron, but if not adventurous and this is indeed issue, then either repair or replacement is needed. Unfortunately, when dealing with RokuTvs, all warranty is done through the manufacturer of the TV. (https://www.hisense-usa.com/television-1-year-warranty) One year for US, 2 years for the Brits/UK.