Why did Lisa reschedule?
If every available agent DECLINEs an appointment, Lisa will alert the prospect. After that, she tries to reschedule them. This experience can frustrate for prospects, who then complain. Their reports go into feedback about the property. If Lisa detects a pattern she may reach-out to agents or bosses to see what is wrong. Agents can block their calendars when they're not available: that way, Lisa knows not to offer times where people are busy.
Even if no agent ACCEPTs an appointment, Lisa will still send the prospect. She knows that agents are on-site during working hours.