I would highly suggest reading this topic as there are a few nuances to be aware of while using network drives.
The best way to use the complete UNC path (\\server\mapped path) and enter the user credentials in MCEBuddy for the path by clicking on the user icon next to the path name. If you’re using mapped drives you need to ensure it’s available to MCEBuddy as it runs in kernel/system space and mapped drives only exist in user space.