I can insert a textarea on my UI, and it shows up just fine.
If I go to Response mapping on the rest service I have and make a mapping to the text of the this textarea, then the field disapears from my UI when I run it for Test?
If I attach som javascript to the field, for when the service responds, it is never run, but if I test the service then everything looks ok.
When you run the app, do you see anything on the screen or blank completely?
The UI looks correct, but the textarea is not drawn if I make a Response mapping in the service to the text property of the textarea. If I remove that mapping, then the textarea shows up when I run the test
Please attach a screen shot with the mapping to textarea.
This is how it looks. 
Try this:
Delete and then set the mapping again
Try mapping a different response parameter
In Add JavaScript, print the value that's being mapped.
If nothing helps, please share the app for collaboration with a href="mailto:support@tiggzi.com" rel="nofollow"support@tiggzi.com/a
I have tried all these things you suggested before making this post :-/ how do I share the app for collaboration?
Close the builder, Options box Share.
Should I then in invite user just use a href="mailto:support@tiggzi.com" rel="nofollow"support@tiggzi.com/a?