In a typical process group, this is how it works. The leader is not really involved or active. Instead, the direction of session is up to the group members.

If they are not talking, it will be difficult to expect any change on that front... or only with time. It depends on the group but usually once people become comfortable, then you will see 'characters' emerge, increased participation and they will react to one another.

If you want to get better at socialising, how about you take the lead? Take the initiative to 'nudge' them rather than retreat further. The group dynamic will change and you will be working on your initial intent at the same time.