What happened
The dashboard surfaces failed mail at the top of "Needs your attention" because a dispute that never physically mailed is a clock that never started.
A failure is almost always the mail provider rejecting the address or being temporarily unavailable — not something wrong with the letter itself.
What to do
First check the client’s mailing address for an obvious problem: a missing unit number, a wrong ZIP, a PO box where a street address is required.
There is currently no self-serve retry control. Contact support with the client id and the round number and we will requeue it. We are told about permanently failing jobs automatically, so we may already be looking at it.