It's not only the Cell Styler widget; the Microflow Timer widget is also no longer working.
Both widgets show me a 'red cross'.
Quite a few add on widgets to display the "red cross" instead of the expected 'blue pyramid' when used in MX10.xx
However this not always mean the widget is not working anymore. Some (like the TabPageSelector) seem to be working fine.
Checking the widgets in Studio Pro shows no problem and all of them build fine when creating a deployment package.
Reply from Support
I wanted to update you on the issues you reported. The issue regarding the red cross will be fixed in Studio Pro version 10.14.0. As for the second issue with the CellStyler widget not working, it has already been resolved in version 10.12.2 and will also be addressed in version 10.14.0.