If the update won’t be installed or continue, you can do an alternative way of updating by performing an in-place upgrade installation by using the Media Creation Tool . Using this installer will always get the latest version of Windows 10. The latest build is April 2018 Update (version 1803).
To know how to do an in-place upgrade, you can visit this link: How to: Perform a Repair Upgrade Using the Windows 10 ISO file and follow the instructions given by out MVP Andre Da Costa.
You can also watch this video: https://www.youtube.com/watch?v=9BWh0YRmnT8 for step by step instructions.
Let us know if you need more help regarding with this in-place upgrade process.