This morning I got a message about v6 upgrade, but when I long press on light, the only option available in the menu is sync. The watch syncs successfully with Connect but I'm unable to access the menu.
Yes, a lot of user (when not all) have lost their controls after the update. After you access the Controls Menu (so this long press on light), then long press up/menu and there will be "Controls Menu" access it and you can add controls again to the controls menu.