This is because the TeamRaiser was created with an eCommerce store number, but did not check the box in Event Advanced Options e. eCommerce next to 1. TeamRaiser eCommerce Enabled:
1. Create a TeamRaiser
2. Go to event options > Advanced Options > eCommerce > Step2. eCommerce Store Associated With the Event Products:
3. Make sure there is no store number if eCommerce is not enabled.
This may also happen if the following options are enabled "TeamRaiser Ecommerce Enabled" "Participants Can Receive Credit for Product Purchases" "Teams Can Receive Credit for Product Purchases"