In docs, fly regions do not match fly platform regions.

[ignoramous]

Dup:

Source of truth for regions

Good question! I can confirm that fly platform regions is the definitive list of regions where you can deploy. I’m not sure why you weren’t able to deploy a machine to den; as one of the newer regions it’s possible machines aren’t supported there just yet. Thanks for letting us know, and for pointing that out about the docs.