There are a few ways to determine if someone has blocked you on Instagram:
Search for their profile
If you search for their username and their profile does not appear, it’s possible that they have blocked you.
Check your messages
If you have previously had conversations with the person and their messages have disappeared or you are unable to send them a message, they may have blocked you.
Check mutual friends
If you have mutual friends with the person, you can check their profile to see if they are still following or interacting with the person who may have blocked you.
Create a new account
You can also try creating a new Instagram account and searching for the person. If their profile appears when you search from the new account but not from your original account, it’s possible that they have blocked you.
Note that there are other reasons why a person’s profile may not be appearing, such as if they have deactivated or deleted their account. Therefore, it’s not always a guarantee that someone has blocked you if their profile is not visible.