the first thing the IRS wants you to do is to contact your employer.
normally the next step, if you don't get it, is to report the employer to the IRS at 800-829-1040. however, the IRS isn't even taking calls at the present
so that leaves you with filing form 4852 with your return. at least some versions of TurboTax have this form. if not you'll need to use the paper form from the IRS and file by mail
https://www.irs.gov/pub/irs-pdf/f4852.pdf
