You can't do that. You have to enter all your income on the same tax return at the same time. Now you have to Amend.
If the IRS accepted your first return, then you have to wait until it has been fully processed and you have received your refund or paid the tax due. THEN you can prepare an amended tax return 1040X and mail it in. You cannot e-file an amended return. Meanwhile, DO NOT change anything on your return until you start the amended return. If you did change or add the missing info then take it out and put your return back to the way it was when you first filed it.
You can check your efiling status here,
How to amend an Online return
What? Do you mean you already e-filed a tax return with a W-2 and then you tried to e-file a second tax return with another W-2? You cannot do that. All of your income is supposed to be on the same tax return. So your second "return" was rejected. You cannot e-file twice.
You have to wait for the first return to be fully processed and then amend it to add the second W-2. Do not try to amend before your first return has been processed or it will cause more confusion and delay.
ALL of your W-2’s and/or 1099’s were supposed to be on the same tax return. Remember that next year and do not e-file until you have everything. Now you have to prepare an amended return to add that W-2—and the process will take months.
A 1040X cannot be e-filed. It must be printed and mailed. It will take about 4 months for the IRS to process an amended return. It is a good idea to use a mailing service that will track it, like UPS or certified mail, so you will know it was received.
Wait about 3 weeks from mailing and you can check the status of your amended return: