Try J:\ instead of J: – it may be that a CD J:\some\other\directory or equivalent had been executed at some point in the past, so Windows thinks the current directory on the J drive is different than the root. By using J:\, you are saying “ignore current directory, and instead enforce starting at the root of J drive”
With a Directory of L:\bin , where L: is a shared network drive, I was able to find 1124 hits in 84 files of 146 searched for the text I was looking for, using v8.5.2
Also, you might want to make sure that Notepad++ currently has access to a file in the J: drive – for example, do File > Open and navigate to a known readable file on J: .