I believe you are saying that your new wife claimed her 2 kids, not your mother. Yes you should file a Joint return in 2024 and you can claim all yours and her dependents, your mother and your wife's 2 kids. They are not separate dependents, they are all yours now. That shouldn't be the reason it rejected. There should be a reject code or message probably in the reject email. Did your wife file a 2024 return by herself? Or did the kids father claim a kid?
A common reject is for the wrong 2023 AGI. Did you enter your AGI and her AGI? Try using zero for the AGIs. The IRS might have processed a return late so the AGI didn't get entered in time. Especially if you mailed it. That works for most people. See,
https://ttlc.intuit.com/community/rejections/help/what-if-i-entered-the-correct-agi-and-i-m-still-ge...
How to correct the AGI in the Online version
https://ttlc.intuit.com/community/agi/help/where-do-i-correct-my-agi-in-turbotax-online/00/26311
If you can’t get it to efile you will have to print and mail it.
https://ttlc.intuit.com/community/printing/help/how-do-i-print-and-mail-my-return-in-turbotax-online...
Be sure to attach copies of your W2s and any 1099s that have withholding on them. You have to mail federal and state in separate envelopes because they go to different places. Get a tracking number from the post office when you mail them for proof of filing.
