It may be because of double quotes.
Try be replacing [var.tbsMessage] with '[var.tbsMessage]' in the snippet.
Byt I suggest you should use parameter magnet:
| <div>[onshow.tbsMessage;strconv=no;magnet=div]</div> 
 | 
or 
| <div>[onshow.tbsMessage;strconv=no;magnet=_]</div> 
 |