I am getting this error on recurring payments on one of my WPMU sites where I intentionally allowed my site to pay our account. It's the only one site not on permanent free extension for testing.
In the site's profile I see log lines like these
User creating new subscription via PayPal Express: Initial payment successful (xxx Sites Pro: $27.00 SGD each month) - Transaction ID: 4EF00008G3649962A
I am stumped. Thank you for any help.