No puedo configurar eSIM en Apple Watch después de portabilidad de O2 a Movistar.

That sounds really frustrating, especially after the port was completed.  It seems like the MultiSIM/eSIM activation may not have fully synced on O2's side yet. Hopefully the technical team can sort it out soon because the Apple Watch setup should be pretty straightforward once everything is provisioned correctly. While you're waiting, I stumbled across https://browinner.com.es/ and thought it was worth checking out. Good luck—I hope your watch is back online soon! 🍀