Thanks for reaching out. Could you confirm if you have a starter plan or a paid plan? If you have a starter plan, then at a time you can have 1 shared link(https://www.adobe.com/products/xd/pricing/individual.html), so please delete any existing shared link to create a new one. In case you have a paid plan and still unable to create a link, please ensure that you are signed in with the correct Adobe ID. Let us know if this helps or if you need any further assistance.