You cannot see a direct list or notification on Instagram that shows who blocked you. However, there are several ways to determine if someone has blocked you:

• Search their username in the Instagram app. If their profile does not show up in search results, you might be blocked or they may have deactivated their account.
• If you can find their profile via previous conversations (DMs) or comments but see no posts and the follower/post counts are missing or it says "No Posts Yet," it is a strong sign of being blocked.
• Use another Instagram account or ask a friend to search for that profile. If it appears there but not on your account, you have likely been blocked.
• If the person's profile appears as "Instagram User" in your DMs with no profile picture or posts, this also indicates a block.
• You also won't be able to tag them in comments or posts if they've blocked you.

In brief, Instagram does not show who blocked you outright, but by checking profile visibility, search results, DMs, and using other accounts as a comparison, you can conclude if you are blocked by a user.