When a ShareLink Option is set to “Multiple” and the link is sent to multiple individuals via email everyone that receives the email can access and perform actions, upload/download, on the shared folder or file.

If the ShareLink option is set to “One-Time” then the first person in the email group to access the ShareLink and perform an action, upload/download, will cause the link to become invalid.

Everyone else who accesses it after that will get a “This link is no longer valid” message. If the first person returns to the ShareLink a second time they will also get the "This link is no longer valid” message.