This means that the applied force is not transferred to the supports due to some modeling issues, i.e. instabilities. If you could attach your model, we could try to find more specific reasons of this issue.
All the reactions of the governing load case of the specific node should be used in the design of the foundation. You might use STAAD.foundation or STAAD Foundation Advanced for the design of the foundations. The reactions of the selected load cases from STAAD.Pro into STAAD.foundation or STAAD Foundation Advanced can be transferred automatically.