ROBOCALL SCAMMER!!! Picked up phone and got a recorded robotic message making vague statements about a "second attempt call" and "federal action" saying I needed to call back or face "significant fines" and something about a "magistrate judge." Very obviously fake, and probably one of those money order scams.
DON'T PICK UP FOR THIS NUMBER, and whatever you do DO NOT CALL BACK.
Don't bother, it's a SCAM. It's either the IRS/US treasury scam or a fake debt collector. Either way, these thieves will try to convince you, no, scare you, into sending them money. It's a SCAM SCAM SCAM. Read about the scam and fake debt collectors here:
https://www.irs.gov/uac/newsroom/irs-repeats-warning-about-phone-scams
https://www.consumer.ftc.gov/articles/0258-fake-debt-collectors