Any Bitcoin transaction with less than 10 sat/byte (not sat/vbyte) can not be freely accelerated by ViaBTC acceleratator, the paid one may become the only choice at times, and of which not also recommended because of high fee that will be demanded by the paid accelerator.

It is better to use electrum, making sure the transaction support replace-by-fee, even if the transaction has a very low fee, it can easily be pumped to any higher fee amount. Pumping the fee is the best choice.