[Vuejs]-Update data when value changes Vue Js

It was in fact a Caveat.

Vue cannot detect the following changes to an array:
When you directly set an item with the index, e.g. vm.items[indexOfItem] = newValue

I changed
this.clients[clientIndex].siteCount= 0
to
Vue.set(this.clients[clientIndex], 'contractsNr', 0)

Updates when the data comes in perfectly now.

Thanks Jacob