Here's super-summarized guide on how to troubleshoot issues you may have been experiencing with your scheduler and booking slots.
Troubleshoot Availability
Navigate to 
AI Scheduler → Availability
Check if Availability days and hours are set correctly
Check have you added to Event where you expect to get calls
Check is proper time zone set
Check if there're any Override dates added
If none of these four didn't solve the issue you're experiencing, proceed to the next step.
Launch Availability Troubleshooter
In case you're already in 
AI Scheduler → Availability menu:
Navigate to "Launch troubleshooter" button above time zone and click on it
Select Events you would like to troubleshoot, leaving "All Events", set by default, or selecting a specific Event, and hit Apply
You'll be able to see following details:
Day start and day end hours → Those are the hours set in the left side. The report will show you calendar events that are impacting your availabilities
Meeting participants
Source for the blocked Availability →
iClosed: availability taken by an Event from iClosed scheduler
Calendar: availability blocked by Google Calendar Events, placed outside of iClosed
Event details → picked up from the iClosed Event name
In 99% cases Availability Troubleshooter will detect what's blocking your availability and in most cases those will be events from secondary/private calendars. If that's the case, please proceed to next step and see how to prevent secondary calendars to keep blocking your availability.
Troubleshooting Calendar in iClosed
Navigate to
AI Scheduler → Calendar Connectionsclick on Check for conflicts
See if you have other Calendars to check against conflicts
Turn off Secondary calendars to prevent blocking availability
In case any of the personal slots are blocking your availability (overlapping with event slots), but you wouldn't like that to be the case, follow steps bellow:
Locate the event in your secondary/private Google Calendar and click on it
Click on the "Pencil" button to edit
make this event "Free", instead of "Busy"
Hit "Save"
In case you weren't able to find the cause for the blocked slots, please reach out to our Support team via chat button in bottom right corner of the screen, and we'll investigate it immediately from our end.