A task was scheduled, the time passed, and nothing was sent. This article covers the usual causes, roughly in the order worth checking them.
First, a quick check: is the task still there, or did the whole sequence stop for that contact? Those are different problems. If the sequence stopped, see Why did my sequence stop? instead.
If it was a LinkedIn task
Your LinkedIn session was not refreshed. This is by far the most common cause. Crono runs LinkedIn automation through the browser extension, and the extension needs a live LinkedIn session to start. Open Crono and LinkedIn in the same browser each day and the automation will run for that day.
You hit the daily limit. Crono caps LinkedIn automation at 50 tasks a day on a standard LinkedIn account and 100 a day with Sales Navigator, to keep your account safe. Anything over the cap is postponed, not lost. You can see and lower these limits under Account Settings → Integrations → Browser Extension.
The contact has no LinkedIn URL, or an invalid one. A LinkedIn step cannot run without a valid profile URL on the contact.
If it was an email task
The sending mailbox is disconnected, or is not the one the sequence expects. Open the sequence and check which Sending email is selected, then confirm that mailbox is connected under Account Settings → Integrations → Mailbox. A sequence uses the address configured on it, not simply your default one.
The mailbox hit its daily sending limit. Each mailbox has its own daily cap, set in the same place.
The address is marked invalid. Crono will not send to an address flagged as invalid, including one that previously bounced.
Causes that apply to any channel
The step is automated but has no template. An email or message step can only be automated once a template is attached to it. Without one, automation cannot be switched on and the step waits for you.
A variable had no value. If the contact is missing data a template variable needs, Crono holds the task and shows a Missing template variable warning rather than sending something incomplete. Fill the field on the contact, or remove the variable.
Contact Data Validation skipped it. If the sequence is set to enrol contacts but skip tasks they lack data for, Crono bypasses that step and moves on. This is working as configured — check the sequence's data validation setting.
The contact is marked Do Not Contact. Blacklisting a contact stops their sequences and clears their open tasks.
A To-do step is waiting on you. A To-do inside a sequence blocks the steps after it until it is completed.
It was simply not due yet. Two things move tasks later than people expect: weekends are excluded from step delays, and Crono spreads tasks scheduled for the same hour rather than firing them all at once. If more tasks are due than can be sent safely in the window, the remainder move to the same time the next day.
Still stuck?
If none of the above explains it, get in touch and tell us the contact, the sequence and the date the task was due — that is enough for us to trace what happened.