Typically, amended returns must be filed within 3 years after you filed your original return or 2 years after the date you paid your tax, whichever is later. Unless the IRS is requesting you amend your return, it is beyong the allowable period to amend a 2019 tax return.
Please refer to this link from the IRS for guidance to help you determine if you need to file an amended return. If you have received a notice from the IRS, you should refer to the instructions on that notice for guidance.