The operation Elements cannot accept the argument error CloudDB

Hello, I seem to be having a problem with my Chat Application made using MIT App Inventor.
Whenever I try to send a message in my chat application, it returns this error:

Here is the code:

You have to trace back that global variable chatHome.

It does not contain a list, only a piece of text.

I made it like this:

Now follow it forward, covering every place it gets a new value.


Read all your blocks.

It's a tough job, but some one has to do it.