Make sure you are logged in as an Admin. Only Business Admins can add partner access. If your role is Employee or lower, ask your account admin to complete this step.
First, check whether Runnr.ai is listed as one of your partners for your business portfolio here:
https://business.facebook.com/latest/settings/partners. If this is not the case, add Runnr.ai using this Business ID:1107951426542935
Then, select the Whatsapp account that you want to use in Runnr.ai here: https://business.facebook.com/latest/settings/whatsapp_account/
Go to the tab Partners, and add Runnr.ai as a partner.