Meetings are double-booked
From SimplyMeet.me
There are few possible solutions. In the Calendar Integrations:
Make sure the default calendar is checked for conflicts.
The default calendar is where Harmonizely will add all the booked meetings. To make sure the meetings are not booked at the same time, the default calendar has to be checked for conflicts (the checkboxes near the calendars must be checked). Harmonizely will then make sure the booked meetings added to the default calendar are checked for conflicts when loading your availability on the booking page.
Make sure the calendars you have events in are checked for conflicts (the checkboxes are checked).
Harmonizely will check the selected calendars for conflicts.
Make sure your existing events in your online calendar have status set to "busy".
Here is an example from the Google Calendar: