[mesmark]

It could be their personalities or the class make up (men to women ratio, all men, all women.) it may be they just don't feel confident or they just have nothing to say on the subject.

You could try some speaking strategy tasks. Responding, asking follow up questions, summarizing and checking understanding, clarification questions, etc. That might get them to understand the dynamics of keeping a conversation alive.

For beginners, having a conversation is difficult. They can't keep it up for long and having the same conversation with the same information over and over can get boring. I like to use the Big Town character cards and have the students practice over and over as new personalities. They're also good for talking about people in the third person. The cards have a lot of information so there's less need for students to come up with answers. Instead, they can focus on the English.

In general, don't give up. It could just be a hump you need to get over with this group. In time, it could very well turn around.