If you're unable to send an email and receive the following error:
"Something went wrong preparing your scheduled send, please try scheduling again."
Our Engineering team is aware of the issue and is actively working on a permanent fix.
Workaround
You can use the following steps to successfully send your email:
Open the Prepare to Send window.
Turn Schedule Message ON.
Turn Schedule Message OFF again.
Click Send Now.
This refreshes the send state and should allow your email to send successfully.