VueJS /implicit/callback 404 Locally

I have successfully integrated Okta authentication in my VueJS app, basically just following the instructions and the sample app. On my MacBook in dev mode, it works fine. With production config, it also works on your Azure-hosted testing VM. However, we have an offshore team that is using Windows. For reasons unknown, the /implicit/callback after successful authentication gives them a 404.

http://localhost:8080/implicit/callback

Anyone have an ideas?