Hey ozbrk,
It appears that you're having a problem installing Xcode on your Mac. You interrupted the download, and now it's not letting you to complete it. We're glad to glad to provide assistance.
Log out, sleep, wake, restart, or shut down your Mac - Apple Support -- Restart your Mac and see if you're able to download the installation file.
How to use safe mode on your Mac - Apple Support -- If restarting your Mac didn't allow you to download the app, see if it will download in safe mode. Whether or not you're able, restart normally to exit safe mode.
Please be aware: "When you start up in safe mode, your Mac prevents some software, such as startup items, from loading, and it performs a check of your startup disk. Your Mac may take longer to start up because of the check."
Feel free to get back to us with any questions or problems you may have.
All the best.