Hello,
I am using the rowGroup extension with multi-level grouping. Similar to this example https://datatables.net/extensions/rowgroup/examples/initialisation/multipleGroups.html . The two grouped columns are hidding without issues. However, when trying to hide other columns, for some reason (I have no error message anyway), they won't hide. I used the example with JSFiddle and it does work to hide other columns (https://jsfiddle.net/pnaw0fbj/ where it hides the column id 3).
In my code, I am also using AJAX with a callback processor, buttons, search builder extensions and I have 30 columns (I want to hide most of them, to be used only in the search builder). This is for a intranet page, so I can't show my exact code. If anybody has some idea where to look from where I am, I'd appreciate.
JSFiddles, all of them works and the last represent pretty closely what I have, except the data come from AJAX! That mean clearly something fail somewhere without any warning or error! 
Base Example: https://jsfiddle.net/pnaw0fbj/
Adding Button: https://jsfiddle.net/pnaw0fbj/2/
Adding Search Builder: https://jsfiddle.net/pnaw0fbj/3/
More column count: https://jsfiddle.net/pnaw0fbj/4/
Even more column count : https://jsfiddle.net/pnaw0fbj/5/
Again even more column count: https://jsfiddle.net/pnaw0fbj/6/