This means that either the trade offer is in the process of sending, or the bot has suffered a failure. In which case, you might need to wait up to a half hour for the bot to restart. If you have been stuck for more than 30 minutes, then we suggest you to ask a supporter in the support chat to kick you out from the queue. If support happens to be closed, you can submit a ticket regarding it in the Help and Support forum (you have to be logged in to access it).