Instagram blocks users from searching hundreds of hashtags. Use the Blocked and Banned hashtag search to see the posts that Instagram doesn't want you searching for.
Have you heard of Instagram's "shadowban"? It turns off your post's reach basically, limiting your exposure to only the people that already follow you. You can still use hashtags and shit will look normal to you. When you click through your own hashtag on a post, your photo will pop up as usual, but when any other instagram user searches for the same hashtag that’s linked to your post, your photo/video will be totally missing from the results, while everyone else's are still showing.
Just enter your username.
How instagram will keep this up, I don't know, because there won't be any left to use judging by this updated list of Banned Instagram Hashtags (2018)