You might come across this error in your campaign:
"Connect to Business Manager to Create This Audience - This ad account is not connected to Business Manager. To create or edit a customer file Custom Audience, your admin needs to connect this ad account to a business account."
If you're seeing this error message, you're actually running up against a new Facebook restriction.
In order to create an audience from CSV, you'll need to connect the ad account to Business Manager. If you want to proceed, you can follow these instructions:
To manage an ad account, add the ad account to your Business Manager.
Go to Business Settings.
Click Accounts and click Ad Accounts.
Click + Add.
Choose one of three options: Add Ad Account, Request Access to an Ad Account or Create a new ad account. See below for additional information.
If you choose to request access or add an ad account, enter the ad account ID. Learn where to find the account ID.
Note: Deactivating an ad account doesn't delete the ad account from your business. A deactivated ad account still counts towards your ad account limit.
More on the three options:
Add an Ad Account: Adding an ad account moves it permanently into Business Manager. You must be both the owner of the ad account and an admin in Business Manager to add the ad account. Please note, once you add an ad account and move it into Business Manager, this action can't be reversed. All management of your ad account must be completed within your Business Manager profile. You can't add an ad account that's owned by another Business Manager. If you still want to work on an ad account that's owned by a different business, you can request access to it.
Request Access to an Ad Account: If you request access to an ad account in Business Manager, the admin of that Business Manager can grant you permission to work on it.
Create a new ad account: If you create a new ad account in Business Manager, it'll permanently belong to that Business Manager. Once created within Business Manager, the ad account can't be transferred to an individual owner who doesn't own a Business Manager.
If you can't add an ad account to a Business Manager:
The ad account you're trying to add may have already been added by another business. An ad account can only be owned by one Business Manager. Instead, you can request access to the ad account.
You have already added a personal ad account to Business Manager. You can only add one ad account from your personal Facebook account into Business Manager. Instead, you can create a new ad account in Business Manager or you can request access to another ad account.
You've reached the 5 ad account limit for adding new ad accounts to your business. There's currently no available option to request additional ad accounts. Your ad account limit increases based on your advertising spend.