Hello Nandan,
There are few things you need to take care of when using gx_prompt_text_set. Firstly, you need to make sure your text buffer is statically allocated. Also, it's also best to declare it outside of function scope. This is because gx_prompt_text_set sets a pointer to where text is found. If it's not static, it will be allocated on stack that is usually released before text can be rendered (as GUIX uses deferred drawing).
Secondly, if you're using custom event handler function for the prompt or any of its parents, you need to make sure that unhandled events return gx_window_event_process(widget, event_ptr) instead of GX_SUCCESS, so that default event handler can call the drawing function in case you didn't do so. This is usually best done using swtitch-case statement where you create cases for each event you want to handle and then provide a default block for any events you haven't specified (i.e. signals from child widgets).
Lastly, you need to make sure that GUIX Adaptation framework is actually toggling the buffers. Check if you've enabled the top 2 interrupts for r_glcd module in the configurator.
Regards