You may not have time available
Check your calendar to make sure you have at least 2+ free hours of open slots within your working hours. If not, consider marking your one-on-ones as Flexible to free up more time.
Your settings may need to be updated
Confirm your Focus Time goal is set in Your ideal day:
You may have an out of office or holiday event
Look for any events that may be causing Clockwise to see you as unavailable; holiday, out of office, or all day events with your availability set to "busy".