By default, a single Nosto account can be connected to one store or language version only, while one Facebook ad account can be connected only to one Nosto account respectively. Effectively this means that if you’re having a localised site version with multiple languages, each language version need to have their own ad account on Facebook, which you still can manage as the same Facebook business manager and ad administrator.
In case you try to connect a Nosto account to a Facebook ad account which you have already linked to an existing Nosto account, this might throw you an error: "Account already connected to Nosto, please contact support." Fastest way to proceed is still to create a new ad account on Facebook and link the new one to Nosto.
If you know that you’re not using any Nosto ad features on any of your possible Nosto accounts, this might be an error while removing old references from our system. In such event, or if you need to disconnect your existing ad account from Nosto, please contact support which will manually remove the connection between your ad account and Nosto.
Please provide some additional details like screencapture of the error message and short description what are you trying to achieve when contacting our support as this simply helps us to process your request faster and helps us to avoid any possible errors.