I was confused and thought it was a bug from ViaBTC LOL. I haven't thought about that. I just have checked the site and found out that there's no remaining hourly free tx. BTW, what's their criteria for not accepting new acceleration request until they find new block? Is it because they want some high fee txs to be included in the block they mine? Or just because we have block size limit? I haven't found any such criteria on their site.