There are some possible reasons behind this go through the following checklist:
  1. Ensure that there is enough personnel to automatically be allocated to your vehicles. This can be a problem if there are more vehicles than staff that can man them or if the personnel is in training somewhere else. If you have not enough staff ready, hire personnel or transfer it from another station.
  2. Check the "Maximum distance from vehicle" setting in the dispatch menu and adjust it if it is too low.