I got a notice for backup city tax. How is this gonna work now?

I'm in PA (Pittsburgh) and I work remotely for an employer out in California. I got a letter saying that I didn't pay the city tax I owed in 2022 and 2023. I did some research, figured out the box in my W-2s where I can verify this, and sure enough, it says nothing was withheld. Seems like my employer simply failed to withhold my city taxes. Now, obviously I owe the principal tax amounts, that's understandable. But the issue is they're also charging an exorbitant interest rate as well as a steep "cost of collection." So my questions are:

• Can I get rid of these two penalties? Has anyone been through this before?

• How does it all work, like, what's gonna be the process here?

• I filed using FreeTaxUSA, I'm surprised they didn't catch this. Can they help me here, should I involve them? Be like "hey you guys made a mistake, help me fix this"?