Cannot search key words on external hard drive on mac

I am having trouble searching my external hard drive for key words that I know are part of my file names. Nothing pops up, or randomly sometimes just a few files. I have tried dragging my hard drives in and out of spotlight to be reindexed and it has not worked. I also made a good amount of space free on my mac, so it also should not be because it is too full.

Would really appreciate any help - currently trying to find files so I can make a film in final cut and it is very tricky when I cannot search file names and have to go through all of the footage : )