Hey there! This is a known behavior in Decile Hub. The platform has a built-in filter that blocks identical emails from being sent to the same prospect within 24 hours, designed to prevent accidental duplicate sends and automation loops.

A couple of things that could explain what you're seeing:

• Test email bug: If you sent a test email to yourself using the same template, it can sometimes trigger this duplicate check and block the real send to the prospect. This is a known bug that's been reported.
• Automation: An automated sequence may have already sent the same email content, even if you didn't manually send it.

Quick workaround: Change the subject line by even one character to bypass the filter and send immediately.

If you did not send a test email and no automation is running, this could be a bug worth investigating further. Could you share more details about whether you used "Send Test Email" before attempting the real send? That will help narrow it down!