I must add -- I had a few collections synced via Lightroom Mobile from Lightroom Classic over the years. None of them have RAWs available in Creative Cloud, not even the new ones I created.
I have 250 Gigs + of photos in Lightroom Classic. Inability of the Classic to upload RAWs to Creative Cloud pretty much kills Creative Cloud for me, I am sorry.
I was having this same problem and I think I know why. However, I'm not sure how to fix it yet
When you sync a photo to the cloud from Lightroom Classic and edit it in Lightroom CC on your iPad, it's just editing the "smart preview which is maxing out at around 2560x1705 resolution. Tap on the screen with two finger to cycle through the "info" on the photo you're editing, it will more than likely say 'smart preview'. If you edit the photo on your iPad, and then let it Sync then go back to your computer with Lightroom Classic you will see the edits have been applied to the "original photo" at the full 6000x4000 resolution and you can export it at full resolution from Lightroom Classic.
I turned off the setting on Lightroom CC on my iPad "only use smart previews" to try to force it to download the original photo when I save to camera roll, but that doesn't seem to work
My guess is the only way to sync the original photo file to the cloud from Lightroom on a computer and work on it using Lightroom CC on an iPad or other device, is to use Lightroom CC on your computer not Lightroom Classic
I hope I am wrong
This is indeed caused by Lightroom Classic only uploading the smart preview. This is a limitation set by Adobe. Here is a feature request asking adobe to add full raw upload to Classic: Lightroom Classic should be able to Sync full raw files to the cloud, not just smart previews | Photoshop Family Custome… that you should add your vote too.