Are you sure the users that you are getting 0 results from are still current users? for example that ‘gg_hashtagneverreload’ doesn’t appear to have a twitch page, and looking up the user with v3 returns {"error":"Unprocessable Entity","status":422,"message":"User \"gg_hashtagneverreload\" is unavailable"} which I assume means that the username is no longer in use (perhaps they changed their username, or the account is banned/deactivated?) as if the user never existed it would have returned a 404 user was not found.
I ran into a similar thing when adding user IDs to my database for v5, in the end I just removed them from my database as without already having their user ID I had no way to verify if they had changed name.