Hi!
Same here with Opera One, with the same context:

Old install: Win10 Pro. New install: Win11 Pro.

Only my pin boards sync, but without any tabs or tab island. I'm erased my bookmarks and most of my tabs moved to Toby.
It's frustrating and time-wasting trying to fix this, when you need to sync your daily workspace to start quickly.

Can't understand why this happens. I hope someone can find a way to fix it. Thank you!

And I hope in next updates make less difficult to manage Opera account data and sync.
For now, it's nothing you can't fix with old fashion methods.