Employees Engagement - how I can motivate employees to be more involved in office activities

I am looking for suggestions on how I can motivate employees to be engaged in office parties. I often find them not responding on time to mails as well. I have shared a survey form with them but have not had fruitful results unfortunately. While the environment of the organisation is good, there seems to be a lack in coordination and engagement.
How can we work on improving the situation?

1. How many years have you been working with current organisation?
2. Why do you think that the employees are not motivated?
3. What sort of mails do you write to employees which they are not responding to?
4. How do the employees gain from filling out the survey form?
5. What do you intend to imply by 'environment of organisation is good'?
6. How did you reach the conclusion that there is lack of coordination and engagement?

Please find my answers below :-
1. I am an associate with organisation since sep 16.
2. Seniors have been complaining that juniors are not working even though they have not been trying to implement new things.
3. Survey Forms, any information related to their work or accounts details etc.
4. If they share their thoughts genuinely then I can try to resolve the issues they might be having. On several occasions I have come up with beneficial solutions for their problems.
5. Most of the people are happy and enjoying their work.
6. Sometimes they are blaming each other for projects given. If and when we organise office parties, many employees do not show interest and fail to turn up.