Scam - not the IRS
I managed to listen to the call. It mentioned a lawsuit.
Folks, the Internal Revenue Service doesn't sue. It doesn't have to. The agency has the power to call your bank and freeze every one of your accounts. It can seize your money through it's own administrative court system. There is no way the IRS would risk losing the case by going through a civil court.
This is a scam.
Don't believe me? Check this bit out from the IRS. And according to this article from a couple of years back, the IRS never uses robo-callers.
That may be a good rule of thumb and not just for the IRS.
Any robo-caller demanding money is almost certainly a scam.