An ArtPro File contains blank/empty separation indices which should be removed (blank separation indices are important for special customers, especially for gravure customers).
Follow these steps to remove them:
First you have to Show Indices in the Separation menu to see the blank separations! This option can be saved with the workspace.
You can select the blank separations and use the left - (minus) button (Remove the selected separations function) in the Separation menu to remove them.
You can drag the blank separations or used separations in the correct order.
If you have blank separations AND also unused separations, you can use the right - (minus) button (Remove all unused separations function) in the Separation menu to remove all blank and unused separations. But this function will not work if there are no unused separations.
If you have blank separations in your one-up and you want to make a repetition, you can enable the AP Preference: Ignore blank separations when placing ArtPro files in the Preferences > Pictures tab and Save the current settings in the Preferences > General > General tab.