UpgradeAdvisor always says that "your phone is eligible for a windows 10 upgrade".
after getting that message, did you check in settings, update?
If no update is available, just try what Maurizio suggested.
- Do a backup first of important data
- Enrol into windows insider program
- Download insider app from store, install it and sign in.
- Select production or release ring and follow the instructions
You're good to go
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