Hello,
Is the computer connected to any domain? Also, are you using the admin account to access your computer? From when is the issue persisting? Do receive any error code related to the issue?
We understand that you are unable to view the contents of the Z drive as it showing permission is needed in that case, please sign in using the admin account, and then follow the below steps.
1. Press Windows key + E key> This PC.
2. This PC> Right click Z: drive> Properties> Sharing> Advanced sharing> tick the Share this folder> Permissions> select the user name>select the full control, change and read as allow.> Ok > Restart your computer.
Please let us know if the issue is resolved or you need any further assistance.
Thank you.
Have a good day!