You have reached your daily send limit
To ensure that you don't run into spam territory, Leadcamp limits your send limit to 250 emails per day by default for all cadence.
You can check and adjust your daily limit in My Settings
You chose a tight schedule
When you set a cadence, you can set what days and hours your emails should be sent. If this is too tight, and you have too many emails that need to get out the door, you may need to adjust the schedule to fit your needs.
Go to your Cadence, to the Preferences section in the sidekick
Click Edit and change the timeframe settings