Invalid object name "x", number 208

Question

I got an error while i run a post command.the error shows

invalid object name 'PatientPastHistorys' number 208.

PatientPastHistorys is my entity. i dont know what im missing.

code

 public JsonModel SavePatientPastHistory(PatientPastHistorysModel patientPastHistorysModel, TokenModel tokenModel)
        {
            PatientPastHistorys patientPastHistorys = null;
            if (patientPastHistorysModel.Id == 0)
            {
                patientPastHistorys = new PatientPastHistorys();
                AutoMapper.Mapper.Map(patientPastHistorysModel, patientPastHistorys);
                patientPastHistorys.CreatedBy = tokenModel.UserID;
                patientPastHistorys.CreatedDate = DateTime.UtcNow;
                patientPastHistorys.IsDeleted = false;
                patientPastHistorys.IsActive = true;
                _iPatientPastMedicalHistoryRepository.Create(patientPastHistorys);
                _iPatientPastMedicalHistoryRepository.SaveChanges();
                response = new JsonModel(patientPastHistorys, StatusMessage.PatientPastMedicalHistorySave, (int)HttpStatusCode.OK);
            }
            else
            {