Wishlist games number became zero after syncing.

same thing

I had the same. I changed my games privacy setting to public (in edit profiles on steam). When I sync'd again with Steamgifts my wishlist came back :)
Edit- it is Game Details under Privacy Settings

Yep same here :/

Oh my bad just needed to change the new game privacy setting XD

thanks fixed it.

Due to recent changes in steam privacy settings as Delisper said you need change the view games to public in privacy settings for SG to synchronise

There are new privacy settings on steam, they are set by default to not display that information to the public so the site can no longer see it. You need to change the setting to public and resync here.