I don't believe you can sync the favorites.

If you are in the US or Canada you will get the program guide in the web browser instead of a favorites guide.

You can try tricking it like telling it you are in the UK and then running the setup program.

To use Watch on Slingbox.com Favorites:

1. Launch Watch on Slingbox.com. There's a link to the right for your convenience.
2. Connect to your Slingbox and begin watching.
3. Toward the upper-right corner of the viewing window, click Pop Up Player.
4. You may be asked if you'd like to open the Pop Up Player by default. Answer however you wish.
5. At the bottom of the Pop Up Player window, you'll see a heart icon. Click it.
6. If you have no Favorites already set up, click the Channel No. box and type a channel number, then press the Enter key.
7. If you do have Favorites already set up, you'll see them listed.
8. To delete a Favorite, move your pointer over it, and click the X in the upper-right corner of the Favorite.
9. To hide the Favorites list, click the X in the lower-right corner of the Pop Up Player.

Note: Favorites are only available in the Pop Up Player.