There are numerous reasons for this. You can determine the cause by interpreting the label. Here are the most common ones. · PAST – The time slot is unavailable because it’s in the past and can’t be booked. · GROUP – The time slot is unavailable because the group event has reached the maximum number of members. · EVENT – Someone has already scheduled the same event type during that time. · CALENDAR – You or one of your team members already have a meeting scheduled at that time. · DURATION – The event lasts longer than the time you’re available.