I started getting this error a few years ago when I was using PSE 14. I thought maybe my computer and software were too old, so I bought a new computer and PSE 2018. Still got the error. Gave up on scrapbooking for a couple years, then thought maybe it was a glitch and tried 2020. STILL getting the error. The thing is--there's no way this file is even close to 2 GB. There's just not that much stuff in it. It's a basic template with some layers in it. And if I know how to read PSE (maybe I don't), the size in the bottom left-hand corner clearly states that this file is 37.1 MB--nowhere near 2 gigs!
I'm utterly baffled about what could be causing this. I just want to be able to scrapbook like I used to for years and years!
You have a very complex document with many pixel-rich layers. It is therefore quite possible that when it is being saved to a psd file, it exceeds the 2GB limit (and the document size shown in the status bar is not showing the saved sized). I just did a quick test and a file containing only 2 simple layers was saved with a size 1.5x the document size shown in Elements.