Is there a time lapse before he can file? Or something special he will have to do now? He has filed for an extension and it was accepted.
He should just print, sign and mail his own tax return, or he can try getting an IP PIN from the IRS to see if that will help him e-file.
https://www.irs.gov/newsroom/irs-takes-steps-to-help-prevent-refund-delays-by-accepting-duplicate-dependent-returns-with-an-ip-pin-for-2025-filing-season-taxpayers-encouraged-to-sign-up-soon-for-ip-pin-online-account
https://www.irs.gov/identity-theft-fraud-scams/get-an-identity-protection-pin