Grid coro not displayed

I have created a combobox using xml in a subgrid which displays the option text from the value correctly.
The problem is that the combobox itself is not displayed so the options cannot be selected & changed. What have I missed?
Code is built with php

<?xml version='1.0'?> Options $footer $name $parent_row $default Hide Read Write

Unfortunately the issue cannot be reproduced locally.
Please, note that the defining option collection for the individual cell is available in PRO version only.
Please, try to define the collection for the whole column. If the issue still exists - please, provide with a complete demo, where the issue can be reconstructed locally.

Thanks for looking
I have tried as a column header and the issue is the same.
Also I am told that we are running the pro version.

Please can you tell me how to double check the version we are actually running?
I really wanted to check that it should work with sub grids.

I will try and create a standalone test but it could take a while.

the version of your dhtmlx you can find in “readme.txt” in each components directory.
for example: