Vimium is missing the "all hosts" permission.
Firefox requires users to manually grant this permission to extensions. You can enable it via
the button below:
Or by navigating to:
about:addons > Vimium > Manage (click the 3 dot menu) > Permissions >
Enable the "Access
your data for all websites" permission.
See here for more info about this permission.
All Vimium keys are enabled on this page.