If a user’s invite has expired and they click the Activate Account link in their email, they will be sent to the following page where they’ll see this message:

Once the user clicks the Activate Account link in the expired email, all admins in your organization will receive an email request from that user asking for access to Chalk.

When you click See Request, the Requested page in the Chalk Admin Center opens.

From there, you can accept the request and a new invitation will be sent to the user.