I have built a fairly large model. During the process of building the model everything has gone very smoothly until this:
The very first nested item group in my model does not want to expand after being collapsed. I selected the item group and have tried each of the three methods available to expand a previously collapsed item/item group. Nothing works. Seems like a bug. All the others expanded nicely.
If you have two or more categories in the row or column tray you can use select/shift/select to collapse a specific instance of an item or range of items. In the attached example I have used this technique to collapse only the instance of B2 which relates to C2 (as opposed to a simple collapse of all instances of B2).
In this case, if you want to uncollapse that particular item (or group or range of items) you must again shift/select the specific combination before the uncollapse option will become available.
This may be the issue you’ve run into and hopefully this approach will help. Please let us know if you have further questions.