The airlock isn’t always the best way to determine the fermentation activity.
So, if you find that it isn't bubbling, it doesn't mean that the wash isn't fermenting. If you open the lid and check the wash is bubbling, that is an indicator that the process has started. Within 24 hours, carbon dioxide should start bubbling through the airlock, as long as everything is working correctly and if the fermenter is sealed properly.
Fermentation can take as little as 3 days if you are using a fast-acting yeast and the temperature is ideal. In cooler weather it can take up to 7 - 14 days.
For the first 24 – 48 hours, heat is generated by the fermentation process. After this period a heat pad or heat belt can be used in cooler weather to maintain the temperature. Do not use a heat pad/heat belt in the first 24 – 48 hours.
Going forward if you cannot see anything bubbling, check to make sure the seals are tightened properly.