How do you know if someone blocked you on instagram?

If you want the bottom line without the fluff, here is how you spot a block. First, try searching their exact username; if they don't show up for you but appear on a friend's phone, you’re blacklisted. You can also check your old DMs because if their name changed to "Instagram User" and the profile picture is gone, the connection is severed. Another dead giveaway is visiting their profile and seeing "No Posts Yet" even though the header says they have a post count. If you try to hit the follow button and it immediately bounces back to the original state, the system is rejecting you. For a final audit, try their profile link in an incognito browser; if the page loads there but gives you an error while you're logged in, the block is confirmed. It's essentially a silent termination of your digital contract with that user. 
I once thought a client ghosted me entirely until I checked their page from my Instagram business account and realized they had only blocked my personal handle.