Facebook limits each Pixel (or “Dataset”) to 3 ad accounts by default to prevent misuse.
Here’s what you can do:
Request More Slots:
In Business Settings, select your Pixel, click Assign Ad Accounts, and you’ll see an option to Request Increase. Briefly explain why you need extra accounts (e.g., you run ads for multiple brands or regions).
Create a New Pixel:
If you can’t get an increase approved, set up a separate Pixel for the new account. Just note you’ll lose historical data and audiences.
Consider Conversions API:
This can pass events without being limited by Pixel connections.
So, the 3-account limit is normal. Try requesting more access first—it usually works if you have a legitimate business reason.