The prospects in the sequence are showing as Active, but not sending. When viewing the sequence information on the prospect, a message shows, "User exceeded their Org's daily email in/out limit. This limit is defined in your Org Settings in Outreach."
To resolve the issue, raise or remove the limits shown below, which you can find by clicking the gear icon in the lower left-hand corner, under Organization, click Org info, then choose the Email tab.
This issue occurs when the user hits the org email limits. It is important to note that these limits shown below include inbound and outbound emails, as well as synced emails to the platform but not sent using Outreach (i.e. not using the Outlook add-in or the Outreach Everywhere Chrome extension).