This means your PayPal Main receiver account (email) (if Business is different from your main account): and PayPal Business (email or secure merchant ID): are not correct.
Example:
You have 2 emails on your account, email1@mysite.com and email2@mysite.com.
email2@mysite.com is set as primary in paypals settings. You would then need to use the following settings.
PayPal Main receiver account (email) (if Business is different from your main account):
email2@mysite.com
PayPal Business (email or secure merchant ID):
MERCHANT ID