Have you worked through the suggestions on this IRS page? - https://www.irs.gov/newsroom/irs-can-help-taxpayers-get-form-w-2
NOTE: this page was written for 2017, so adjust the years accordingly.
At this late point in tax season, you may want to first file an extension (4868), then request a Wage & Income Transcript from the IRS - https://www.irs.gov/individuals/get-transcript. You may be able to get the transcript online. The transcript should give you your W-2s (that were copied to the IRS) and allow you to file.
If you never received the W-2s and the IRS hasn't either, then report the employer to the IRS as described on the first link, but first take care of yourself - as the first link says, try to get the transcript of the W-2s and file.