A participant who you had invited to a previous time had declined, but you've managed to discuss a new time that works.
To re-invite them, you simply follow these steps:
Select Filter ➡️ Select Name ➡️ Type in the participant's name
Once the name appears, click on the Dropdown button next to the Status
Select Invite and go ahead and pick a time that was agreed between you & the participant
If the time that you have agreed with the participant does not already exist in the Calendar Tab, you will first need to add that session in the Calendar before re-inviting them.