I guess because that folder does not exist on your machine?
If you click on 'Edit' it will show you where it expects it to be (on my Windows machine e.g. in "C:\ProgramData\Processor Expert\PEXDRV_PE5_3").
Such a legacy folder was used for Processor Expert 'legacy' components before the introduction of the Processor Expert repository concept (see Processor Expert Component Repositories | MCU on Eclipse ).
I hope this helps,
Erich