I would try deleting your Social Security entries and see if the error goes away. If it does, then go back in and try entering them again and see what happens.
I tried deleting the Social Security entries and then re-entered the data. That did not resolve the issue. Client had similar data last year but no corresponding error message requiring attaching copies of their SSA-1099s.
Is this a new IRS requirement, or a bug in Lacerte?
After further research, Colorado did in fact change the requirements when claiming a deduction on the 2023 Colorado tax return related to social security income taxable on the Federal return. Including copies of taxpayers' Forms SSA-1099, when filing the Colorado tax return electronically, did not exist prior to 2023.