Hi there! We'll try to help however we can. I do need to say right off that bat that we
do not support CIO, which is what you used earlier for your LO. It is very traumatizing for your child and ultimately, is not usually long-term effective, as all you've taught your child is that you will not come when they need you.
The 2-1 transition can be a slow process, and varies for each child. With DS1, my aim was a nap from 1-3 so I kept pushing his morning A time by 15 mins every 4/5 days, and I chose to cap the morning nap and give him a nice long stretch in the afternoon, as that's when he really needed it. I remember that once he made it to 11:30, he did a massive leap and stayed awake until noon. From there it was much easier. However, while this whole transition was going on, bed times were a little wonky as we tried to do early bed times whenever things went sideways. We finally decided to make bed time the same consistent time it always had been, and let that, and morning wake up, be his constants. When we made that commitment, it made a huge difference within 3 days. He'd be pretty darn tired by bed time (7pm, eyes shut) but he slept until 7am, and started napping better during the day.
We have a 2-1 transition group in the Naps section of our sleep board and you will find lots of parents going through the same phase as you. Sometimes it's just nice to have other people in the same sticky spot