Welcome to the community, @Tina_Bao! :grinning_face_with_big_eyes: Unfortunately there’s no way to reactivate the previously-assigned URL. Airtable assigns randomly-generated IDs for lots of things: records, fields, tables, views, etc. In the case of a form view, that share ID only lasts as long as the form is shared. Once sharing is disabled, that ID is effectively forgotten, and a new ID is randomly generated when it’s shared again.
If you need to share a form at certain times and have it inaccessible at other times, while not needing to share a new URL every time it’s reactivated, you might consider embedding that form in another webpage and sharing the link to that page instead of the direct link to the form. When you want to un-share the form, remove it from that page.
