Challenge Guide: Issue Tracker - Please Help

I can’t understand why my project can not pass the :

"You can send a PUT request to /api/issues/{projectname} with an _id and one or more fields to update. On success, the updated_on field should be updated, and returned should be { result: ‘successfully updated’, ‘_id’: _id }. "

I found in the database that the document was updated by using the put method.
Could you take a look and tell me what happened?

Link to my project:

browser information:

User Agent is: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.88 Safari/537.36.

Challenge: Issue Tracker

Link to the challenge: