As a manager of a location, you can view all the users in your location from the location tab. Sometimes, newer users may miss or forget about their email invite to expand share. You have the option to resend this invite. From within the location tab, scroll down and click the member section.
This will pull up a list of all users in this location. Any user that has not yet accepted their invite will show an invited tag next to their name, clicking into their profile, then clicking the three dots at the top right of the screen, you can select the invite option. This will send the user a fresh invite to their expand share account, and you will see a confirmation at the top of the screen showing the invite has been sent to this user's email. It's also best practice to remind these individuals whenever you can as invites do expire.
This is how you can ensure your users gain access to expand share.