Bookeo does not sync directly with your phone - Bookeo syncs bookings to Google on your computer, and then your phone syncs with Google. The two syncs are separate and independent.
If you can see bookings synced from Bookeo on your computer, but do not see those bookings on your phone, it means that the sync between Google and your phone is not working. But the bookings are in your Google calendar.
You can find help to fix sync problems with the Google Calendar app in this tutorial: https://support.google.com/calendar/answer/6261951