What exactly does it say you need Schedule 2 for? It has retirement on it in part 2 line 8 Other Taxes. Did you make a IRA contribution or get a 1099R for a withdrawal?
https://www.irs.gov/pub/irs-pdf/f1040s2.pdf
It comes from Form 5329
https://www.irs.gov/pub/irs-pdf/f5329.pdf
