IND-507 error and rejected fed return

[GW201]

I am a full-time college student and could be claimed as a dependent in 2021 by my parents. My parents just filed their taxes and received a 507 error, saying that I was already claimed, even though I double checked, and I did mark the boxes stating that I could be claimed and that someone else was claiming me. Could this be a mix up on the part of the IRS? 

[xmasbaby0]

There could be a mistake---or maybe someone else accidentally (or deliberately) used your SSN on a tax return.   Whatever the reason....when this occurs---the only way your parents can file their tax return that claims you now is by mail.   They need to print, sign, and mail their tax return.

And although you are sure you answered the questions correctly --- look carefully at your own 1040 and see if the box is checked for being claimed as a dependent.   It is up near the top of the form near the words Standard Deduction.