This question has been answered here from `chrisroberts` and the answer is reproduced below:

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Hi there,

This box is externally hosted, and it appears that the account where the box file is/was stored is not currently available. The result from fetching the box file returns the following:

curl https://storage.googleapis.com/arrikto/vagrant/boxes/minikf/20210428.0.1-l1-release-develop/virtualbox/minikf.box
<?xml version='1.0' encoding='UTF-8'?><Error><Code>UserProjectAccountProblem</Code><Message>The project to be billed is associated with a delinquent billing account.</Message><Details>The billing account for the owning project is disabled in state delinquent</Details></Error>

Due to this, it appears that this box will be unavailable.

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