Hello Andy, - I branched your question to a new discussion thread. See below and let me know how you do.
It seems that mapped drive letters DO NOT appear by default - but if you type in U:\ - <mapped letter:\> - it will display the files as you see here.
MAKE SURE that the account that is being used to start the service has the appropriate read access rights to see that server / folder: - specifically I believe it is the engine service.
Click to enlarge
Alternatively you can use UNC path - such as \\share\folder as well:
Please mark the appropriate replies as CORRECT / HELPFUL so our team and other members know that your question(s) has been answered to your satisfaction.
It is not possible to use a mapped network drive in the path.
This is not something that is guaranteed to work and in general doesn't scale very well if you are going to horizontally scale across multi-node. UNC shares will resolve as long as DNS / resolution is in place (if this is broken then you have bigger issues organizationally) and permissions do not change.