Amended returns normally take about 4 months to process and this year will probably take 6 months or more. You need to use the AGI from the original filed 2018 tax return or 0 (zero) if not 2018 return or it was filed late. The IRS only used AGI from 2018 returns that were in the system by the due date.
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**