Hello there @DanHR!
The error you are encountering, Turnkey Error1, means that the Unreal Automation Tool can’t find or use your installed development kits.
The first step here would be to ensure all elements in your install are using the correct version, even re-installing your SDK, following the document below:
Next, please double-check your PC’s name, even update it to a simpler one. Then, perform a clear cache to rule out data corruption, via deleting folders Intermediate and Saved from your project.
Alternatively, this issue was covered and resolved in another thread, please check their methods for your scenario as well: