While waiting for IRS to answer, I came across this on the IRS website: you can use any five digit number except 00000 or 12345 for a self-select PIN. I got the same "reason" you did, but since I had use one of those numbers I thought that might be what they meant to say. So I just now tried a different PIN---I can't yet say that it worked,
but if that's you, you might give it a try.
@djgj9761 If you filed 2017 late or amended, then your 2017 AGI did not make it into the system, so even if you are entering it correctly, you will still not be able to e-file. You can try using "zero" to e-file. If that does not work either, then you have to print, sign and mail your 2018 return.
When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s. Use a mailing service that will track it, such as UPS or certified mail so you will know the IRS/state received the return.