How do I resubmit my 2021 returns if I am told by the IRS to do so because my printed and mailed returns have still not been processed?

If IRS tells you they don't have your 2021 tax return,

You have to print, sign and mail the tax return a second time.

Use the IRS mailing address shown for your state of residence.

@john-shotgunninj 

E-filing is permanently closed for 2021 returns.  The only way to file a 2021 return is by mail.   If the IRS did not receive your return you can print it, sign and date it in ink, and mail it in.  Use a mailing service with tracking like certified mail so you will know they received it.   

When you are in a situation where someone else has claimed your dependent before you e-file, filing by mail is your only option.   The IRS will not accept an e-file with a SSN that has already been used on another return by someone who claimed that dependent.  They will sort it out after you mail your own return claiming your son.  Expect a letter at some point in the future and be ready to show the IRS that your child lived with you.