I'm not sure if its strictly a google translate issue, but many times, when I highlight a chunk or a whole sentence to get a translation, the result in the right panel is an exact copy of what I selected. So, no translation, just kanji & hiragana. I then have to click de "x" symbol next to my selection, and redo the selection. Then it works. Its probably safe to say it happens 50% of the time.
The problem happens in japanese. I use chrome. Dont know if that information helps.
Sorry if it has already been mentionned. I took a minute to google the question to make sure its not a duplicate, but wasnt sure how to formulate it.