There are different types of bans on Instagram. There is the standard one where you would be notified that you have broken their terms and conditions. However, there is also a shadowban which can be harder to notice since they do not tell you. And, since they do not tell you, you would not be given a reason for it.
A shadowban is basically when your current followers can see your posts with no issue but potential new ones cannot. Your posts are not showing up in hashtags, and the explore section of Instagram.
There can be a couple of reasons for this to happen, such as:
Instagram would like users to grow their accounts naturally as well as to complete their goals. This does not mean in the matter of likes but engagement and getting good works/ messages/advice/stories etc. out there. This cannot be achieved by spamming hashtags. Also read, what actually happens when you buy Instagram followers to better understand how well the buying thing work too.
A test you can do is to post something with a made-up hashtag that no one would ever use. This is so that your post can be the only one in it. Then ask five people that do not follow you if they see your post in the unusual hashtag. If they can you are fine. If not you have been shadowbanned.
To get out of the ban you should follow the terms and conditions of Instagram and do not use bots if you are. Another thing to do is to check for broken hashtags and try to keep up to date with this. Bu the best and easiest course of action would be to take a two-day break. No liking, posting, stories sharing, etc. This is said to “reset” your account without you losing anything, and it can give you a chance to research the broken hashtags not to use.