OK.......At some point were you using Beta software on your iPhone? I see you have Beta Updates turned off, but I'm thinking you had them on and that would interfere with updating to the newest public release of iOS 26. I've never, would I ever installed Beta software on my phone. Too unpredictable and can cause update issues when things are released publicly. I'd recommend you contact Apple Support directly for help here. If you're in the US, you can call Apple at: 800-MY-APPLE or if you have an Apple Store close to you, go there and get in-person help.