Below is a suggestion to help you with your problem.
Update your version of N8N first, because new versions have bug fixes.
Here is the link to the documentation that will help you update your N8N
Once updated, follow the step-by-step instructions to integrate NOTION into a new workflow.
Remember to DEPLOY your VPS so that the settings are updated
I hope I have helped in some way.
If this suggestion solved your problem, mark my post as a solution (blue box with check mark) so that this ongoing discussion does not distract others who want to find the answer to the original question and click the heart. Thank you