There are a few reasons why your students are getting this error message. Most likely, the simulation has a duplicate. So, it will be best to check your course if the simulation was added twice may it be published or unpublished.
If you cannot see any duplicate simulation added to your course, please contact Labster Customer Support so that we can escalate the issue to our devs and manually delete the simulation instance to resolve the issue.
Please do not hesitate to reach out to our Support Team if you have any questions or need assistance.
To get in touch with our Support Team, you can:
🔵click on the blue button located at the bottom right of the screen
📚 Help Center article Contact Support
📧 or by email: customer.support@labster.com