Unable to change track icon instruments

I am unable to change icons on a track. Example: Tracked drums last month and during the session did not assign an icon to each individual track (was just going to do that during mix down). Fast forward to today... open month old project - can not change any icons in the project. Yes I now how and where to change them, it is just a case where the software will not allow me to select any other icon. Suggestions? Thank you Logic community in advance. Cheers.