This error could be due to corrupted installation files, an incomplete installation or may be an incomplete uninstall. We also need to consider one thing here if you are trying to do Windows 10 free upgrade. It was a limited period offer. Please check that. If this is not the situation try doing manual Upgrade with Media creation Tool.
Solution 1: Windows 10 Free upgrade not available after limited period offer
Some users have received a free upgrade offer of Windows 10 on their systems. However, this was a limited period offer and was only available until 29th July 2016. People who have received the offer and did not do the upgrade before 29th July 2016 might be receiving this error. So please check if this is the case with you.
Solution 2: Try doing a Manual Upgrade with Media Creation Tool
In some cases where the error code 0x80070015 appears and automatic upgrade is not working, we can try downloading the installation Media manually and then do the upgrade. You can follow steps given below to do the manual upgrade. The tool will start downloading Windows 10. Once the download is complete, it will walk you through the update process This will complete the manual upgrade. During the setup process, your system will restart a few times.
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