Sometimes the Hive nodes have issues.
I also had an issue with a post that had an error while, but still was posted. Peakd also showed me that the post was still in draft although it had been posted.
So always check your posts even when you get any errors because they might still have been posted. Especially when you try it a day later.
As you can see posting multiple times might get your posts downvoted for spamming.