Are you sure you’re logged into your VRChat account?
Please select “Logout” in your System menu and then log back in using your VRChat account. Steam accounts cannot upload or use custom avatars (but can use avatar pedestals).
Are you using the right Unity version?
You must use Unity 2019.4.31f1 as described in the VRChat Documentation. Any content uploaded from a newer Unity version will not be visible in menus.