It sounds like you had an unmatched bet - this can happen. We've written about it and how to deal with it here - https://blog.themoneyshed.co.uk/unmatched-or-partially-matched-bets-matched-betting/it's ok - settled now.
Yikes, sorry I misread! (stupid man flu!)it matched my bet ok, it just wasn't settled. It was settled over an hour after the race ended. Their website has been offline a couple of times this afternoon with tech problems but seems to be back up now.