have they been working for 2 days only?
This transaction accelerator tool has been running since last year. It very recently gained a massive amount of popularity when people were badly struggling with getting their transactions confirmed.
yeah now their service is useless
Basically yes. In a tweet ViaBTC stated that their hourly limit of 100 transactions was reached within 3 minutes, lol. If you want to include your poor fee transaction within their block, you basically need to spam the tool with your TXID and fill in the captcha.