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After further review we have decided to move this thread to a category we think is more appropriate for this topic, as it's troubleshooting on the PC platform.
I fixed it by downloading the installer from my account page and running it instead to install over the game. The installer updated the game without doing a full install.
Make sure you read all the other threads on this page about the launcher not updating, as there are assorted fixes, the most common seeming to be the temporary disabling of Windows Defender Run-Time Protection.