Hi Jim, 

Welcome to Box Community and glad to assist! 

Please get in touch with the file owner to modify or extend the shared link's expiration date.

To set an expiration date on a shared link: 

1. In the Share window, click Link Settings. The Shared Link Settings window opens.


2. Under Link Expiration, click to Choose Date box displays.


3. Click the calendar icon and then locate and click the date you want.


4. Click Save.

When you place an expiration date on a shared link, the file or folder to which the link goes displays throughout the Box interface with a small red clock icon ().

Meanwhile, if this section is grayed out. Please have the owner to reach out to their Box Admin instead.

Hope it helps!