@derju Thank, You!
It worked. The "trick" is very simple and consists in to set the passphrase (pp) IQUAL to Opera user password. Yes, you MUST set a pp if you want to sync passwords and avoid to sign in every time you use the app.
Basically, I managed to sync three different devices by following next steps:
- Activating "synchronize passwords" in Opera Browser (Windows).
- Will be prompted to set the pp. It is Mandatory be equal to user password.
- To sign in at Opera (Android) and to activate "sync passwords".
- Will be prompted to write the pp set before in second step.
- Repeat 3rd and 4th steps for every Android device.
I had read your spanish text reply that was originally the solution and it was deleted by the moderator. Better the language instead the solution?