Try to catch the item you want to select with object spy with point and fix and choosing the specified item and press Shift+Ctrl+A in this way you can see if the class of the dropdown is recognized.
I had the same problem with selecting the dropdown items on desktop application build in Delphi, after adding the class of the dropdown Tools->Current Project Properties->Open Aplication->Text Recognition all items from the dropdown were recognized.
I had also follow the steps from the link Compiling Delphi 2007 Applications With Debug Information and rebuilding new .exe my application is working more fast and stable, the controls are recognized.