Hi Thank you for your reply. No, we are not using office 365. We have SharePoint 2013 server. I found your blog about how to set up checkout/in data connection, but it didn't work for me, when I open the form, it won't check out automatically.
Plus: I think you're right. After I submit a form and reopen it, I got a web service error message. It says, An error occurred while trying to connect to a web service. Any suggestion about this?
Thanks a lot!!