My son didn't check the box for if someone can claim you as a dependent
I claimed him on mine and have been rejected.
Do I have to file an extension until this is resolved.
No, once you update your tax return to remove the Reject code you can resubmit the tax return.
Here’s the link to show you how to "fix a rejected" return:
https://ttlc.intuit.com/questions/1901491-how-do-i-fix-a-rejected-return