According to the Create a transaction page on the Partnero API Documentation, here are the required parameters:
Looks like now you’re using the customer key from the Create a customer module instead of email, so everything seems in order now.
You might want to contact support for this bug. They have access to your specific account details, module code and scenario logs, and internal tools and resources, which allows them to investigate further than what we have access to.
You can open a new ticket, or if you are unable to login for some reason, you also can reach support using the contact form on the website.
If you manage to get your issue resolved with support, we’d still love to hear about it! Sharing your solution on the forum can help others facing similar problems.