The Add to Instantly Sequence button appears on a visitor notification in Slack only if RB2B has identified the visitor's email address. Since Instantly uses email addresses to contact your leads, a valid email address is required for RB2B to send data to an Instantly sequence. If you see the Add to Instantly Sequence button for some visitors but not others, it's because RB2B couldn't resolve the email address for those visitors.
Updated over a week ago