Welcome to the Make community!
It seems that the event doesn’t exist on that calendar.
Make sure that you are using a connection that has access to that calendar, and select the right calendar.
I am able to delete an event on mine:
If you think this is a bug,directly contacting support can often lead to a faster resolution. They have access to your specific account details, scenario and scenario logs, server-side logs, and internal tools and resources, which allows them to investigate more thoroughly than what you have access to. Additionally, sharing sensitive information about your situation might not be suitable for an open forum discussion.
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.
My apologies, it was my mistake. I was connected to a different email, and I was attempting to access another calendar.
Hey there @riya_kumari 
Thank you for sharing this info with us!
Don’t worry we’re all humans and errors and misclicks sometimes happen 