Viabtc paid service always returns an error, I tried the free one, it works perfectly it recognizes transactions, I even managed to accelerate one but the paid one give me an error all the time. It might be because I'm on mobile but I tried desktop view in FF and Chrome and it's still the same.
I just checked that on PC and I confirm that their paid service is not working.
I submitted several transaction IDs with the fee rates ranging from 8 sat/vbyte to 15 sat/vbyte to their paid service and got error for all of them. It only displays a message at top of the screen saying "Error" without any explanation on what causing the error.