Authenticate host with netrc fails with "Issue with input: No Username parameter specified"

We have this step configured to use a GitHub username and PAT from secrets. The step is configured the exact same way for both our CI workflow and deploy workflow. The CI build succeeds, but the deploy fails with “Issue with input: No Username parameter specified”.

It was previously working for the both workflows. I have tried deleting and re-adding the step, adding a new secret variable for the username and referencing that, and a few other things like changing the order of the steps. Nothing helped

Build output for the failing workflow shows nothing listed for username or password. Build output for the successful workflow shows [REDACTED] for username and ********** for the password, so it seems the step is for some reason not populating those variables from secrets. Any thoughts on why this would be?