It seems like other people are getting this same error and I have tried several different ways of submitting that permlink including submitting it like "/@brianphobos/multi-player-2d-arcade-game-to-win-more-steem-steemgalaxy-com" and "@brianphobos/multi-player-2d-arcade-game-to-win-more-steem-steemgalaxy-com"
It seems like a couple submissions got through earlier. Possibly before HF21 took place.