The main reason for drops are periodic updates in algorithms of social networks that influence on stats counters. Unfortunately we can’t predict or affect these processes.
Another common cause is violation of the requirements of the services. For example you chose the wrong GEO or your video is not public. You can find all requirements in the service description.
We advise our partners to use guaranteed services, as we will refill these orders in case of drops!
Please check Viewsta Refill Policy as well.