In order to re-invite the user, navigate to the 'Users' section of the application (this is located in the 'Settings' menu) and click on the three-dot menu next to the User's details.
You'll have to be on the Web App to be able to do this.
Within the drop-down menu, click 'Resend Invitation'. This will send the specified user a temporary login link to access the platform.
That's it, you're all set to re-send invites to users!