I don’t see that, is there an option to turn it on?
Another possible reason why you don't see it (other than having lowered the Verbosity slider), is you are using the menu incorrectly, not according to the manual, which suggest the following workflow at Page 92:
This is now your normal workflow should be:
• Open the GSX menu from the Toolbar icon only when first starting Ground services.
• Don’t close it from the Toolbar while Ground services are performed, always use the Hot-key or the X icon to close the menu.
• Always use the Hot-key to re-open the menu, and always close it either with the Hot-key or the X icon.
• Close the menu using the Toolbar icon when you are done with Ground services, usually before take-off.
If you close the menu with a mouse click on the Toolbar, lots of things won't work, all described in the manual, and missing text messages is one of those.