Wait a little bit longer - you have the USPS tracking history, so there shouldn't be any issue with the IRS saying you didn't mail it on time.
Between the IRS and the USPS, there seems to have been a perfect storm this year - the IRS has been overwhelmed with late changes to the tax code and COVID-related workplace issues and the USPS has been, well, the USPS.
If you haven't seen any delivery notice on the USPS tracking site by the end of this week (May 13?), then print and file the return by mail (again). Include a short letter explaining it is a resubmission because the original return appears to have been lost. Also send it by certified mail with return receipt requested. There really isn't anything else you can do.
