Can't add table row dynamically using webdynpro

Hi Experts,

We're now using Adobe PDF as our form, and we designed the form by Adobe Lifecycle Designer 10.4.0, and embedded it in webdynpro for java(NW7.4).

We're facing a problem that, I can add a new table row dynamically in Preview:

(The left button is a Standard button, and the right button is a WebDynproNative button. Both table has initial 1 row.)

but we can't add a new row after deployed:

Does anybody what's the matter?? Any suggestions are appreciate.