Some mobile hotspots (Verizon and Tmobile, notably) have been configuring their hotspot APNs to use IPv6. Roku devices cannot currently use IPv6, so will need to verify that your hotspot is using IPv4.
Look through your hotspot settings for something that says APN, IP Protocol, or similar language and verify that either IPv4 or IPv4/IPv6 is showing. If showing IPv6 only, will need to change the APN to use IPv4.
Are you using a mobile hotspot on a phone/tablet (Apple or Android) or is this a portable hotspot device?
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