[Help me about dialog box for conversation]

I have a problem when I talk with NPC

If we talk with NPC they will have a dialog box for conversation.

but when I talk, the dialog box shows up for a few seconds and disappears.

after that clicked on the NPC that I wanted to chat.

But I can't.

they show "Any work in progress (NPC dialog,manufacturing...) quit and try again

I try and try it again. But it still remains the same.

I try almost every ways.

Pls help me

I want to know many ways from u all guys.

Thx

//----------------------------------------------------------------

Ps. I can speak english a little bit hope u all will understand me