Hi Satoshi,
I finally can reproduce the issue. It turns out their logic only works when sorting is not active or to be more specific, when there is no orderby or order set as param in the URL. Once sorted with our plugin on a column, we store this as a user preference for the specific overview / layout.
So next time you visit the same overview page or just click on the link left in the menu, you’ll go to the overview page without the order and orderby param in the URL. But in fact, the page is still sorted on the last sorted column by the user last time he/she sorted on a column. You should see the ‘reset sorting’ button on top of the overview.
This causes, of course, a conflict because ICPO tries to sort on their logic, while we still sort on the last stored sorting preference. The sorting behaviour (including preferences) is not something we will change in our plugin, but I believe there is a workaround for you to make both plugins work.
You could create a new column set with our plugin. When you click on the ‘restore columns’ button for that specific column set, it restores the default WordPress columns for that specific column set. You can disable sorting if you like, just to make sure that no other sorting logic than the logic by ICPO is applied for this specific column set. Can you try this and let me know if that works?
P.S. Clicking the ‘reset sorting preferences’ cleans all sorting preferences! You could also do this for the specific overview by clicking the ‘reset sorting’ button on top of the overview screen.
P.P.S. Clicking the ‘reset default settings’ removed all the settings for Admin Columns. I would not do that so often because you WILL have to re-add all columns you already did!