It depends on a lot of things..
1. Your content -- they might not like it
2. Your followers count -- if it's small amount they might not follow you back
3. The users you follow -- if they're not related to your niche, they might not follow back
4. How long you wait before results -- some people don't check their IG everyday, so it might take 2-3 days to see final answer.
My recommendation: do not follow people based on hashtags. I had the worst results that way.. but then again it could be only me.