Thank you for your response.
Yes, the error is causing issues with purchases.
When a course is or has been linked to a Tutor LMS course, it cannot be purchased because the following message appears:
https://vetschoolclub.pl/wp-content/uploads/2025/11/Zrzut-ekranu-2025-11-14-o-10.38.16-scaled.png
“An error occurred while processing your order. Before placing your order again, please check that there are no fees on your payment method and review your order history.”
I had to recreate all products from scratch, avoid linking them to the course, and assign access manually.