One expansion on this. I tried using vserver security file-directory show on the OnTAP command line just to verify I can access the CIFS Server that way, and it doesn't work either. I've tried:
vserver security file-directory show -vserver <vserver> -path /<vserver>/c$/
and
vserver security file-directory show -vserver <vserver> -path /<vserver>/c$/<root_volume>
and
vserver security file-directory show -vserver <vserver> -path /<vserver>/c$/<root_volume>/<share_name>
and lastly
vserver security file-directory show -vserver <vserver> -path /<vserver>/<share_name>
Nothing works. I get "the specified path cannot be used. Reason: no such file or directory". But when browsing in Windows Explorer they are all there!