Before you run the system in Hardware you need to rebuild the system to target the Hardware.
In the simple_application_system.sprj page, change the Active build configuration to Hardware
Add the following options in the Packaging options box:
--package.ps_elf ../../A-to-Z_app/Debug/A-to-Z_app.elf,a72-0 --package.defer_aie_run
Select the simple_application_system and click on the hammer to build the system