@Danp yes, I'm getting this error on the settings > remotes page.
As you can imagine, I'm confused why NFS works on the main SR page, but not the settings > remotes page
EDIT: never mind, discovered that I have to put the full share path, not just the share name.
Example:
\\10.69.50.31:Port:/mnt/user/UnraidBackup/XCPNGBackups