Some people don’t like it when everyone can see who has signed their key, as this might reveal sensitive information about social connections. Because of this, keys that are uploaded to gnewpg are only visible to people who already posess the keys, unless the verified owner of the key explicitly changes its privacy settings. This way, the social connections are only visible to people who the key owner has given the key to.
To prove that you already posess the key, you need to upload it to the keyserver. If you are logged in, the key will be saved in the keyring of your account. Otherwise, you can download updated versions of the keys immediately after uploading, but the uploaded keys will not be visible to you.