It depends.
If the IRS processes the 2018 return before processing your 2019 return, it's possible you will not get a stimulus payment immediately.
The IRS is going to be issuing the stimulus payments throughout 2020, so you may still get your stimulus payment once the IRS receives and processes your 2019 tax return.
When you file your return in 2020, you will have the opportunity to report the amount of the stimulus check(s) you did receive, and if it was less than what you were entitled to, you will receive a credit on your tax return.
What does the stimulus bill mean to you
The payment of the stimulus funds can be tracked at the following website:
At this point you may wish to contact a specialist that can work through that section of the return with you. The specialists can look at your return on their screen to find out exactly what is causing the rejection and suggest how you can take corrective action if needed.