The jam has to be published and unlisted. Is that the issue you're having?
Viewing post in Sending link to unlisted Jam
Hi,
Thanks for the reply.
It seems the only option is as follows, when you set up the jam,
Visibility
Your jam is only visible to you and other admins until published.
- Published — Jam is visible and ready for submissions and ratings when appropriate
- Unlisted — Jam will not be listed on itch.io jams page
Doesn't seem to be any option to have it published and unlisted?