Hi AdelleW,
I'm Dyari. Thanks for reaching out.
If your computer is joined to a domain and you want to have access to QBs data on your Z: drive, ask your server administrator to troubleshoot the issue because he is the only one that knows what the issue is and how to troubleshoot it.
If you are a server administrator, I would suggest posting this query to our sister forum from the link below.
https://learn.microsoft.com/en-us/answers/index...
They are more oriented with regards to this type of issue and there will be System and Server Admins who are available that will be able to fulfil your query as we are more of a home consumer-based forum.
You can also ask QBs support services to provide you with troubleshooting steps.
Have a nice day.