To keep Pinterest running smoothly, there's a limit to the total number of Pins, boards and follows we can store for accounts.
You can have up to:
If you’re already following 50,000 people, you can only continue to follow people who already follow you. There’s no limit to how many people can follow you.
If you get an error saying that you've hit a limit, try deleting some Pins or boards, or unfollowing people.