If you get the error
An error occured while validating the account connection: AuthenticationError.CUSTOMER_NOT_FOUND after connecting your Google account in Matomo Paid Advertising Performance, this is probably because either:
- you are using a developer key that has not yet been approved by Google Ads team,
- or because your developer key is only able to access test accounts but the connected account is a production account.
To solve this issue, please apply for a Google Ads Developer Key and try again to connect your Google account.