Symptoms

Team Calendars for Confluence unable to delete any calendar events in IE and it always leads to "There is an ERROR occurred, Bad Request". Any other Team Calendars for Confluence request triggered without issues, this issue is not reproducible in other browsers. 

Diagnosis

In order to troubleshoot this issue, please take the following steps:

1. Replicate the issue and capture the network traffic
2. Delete the calendar event using a different browser and capture the network traffic
3. Compare the cookies information from both  browser

4. IE cookies show DNT parameter which doesn't exist in the other browser network traffic captured 

   DELETE http://localhost:8090/rest/calendar-services/1.0/calendar/events.json HTTP/1.1
   Accept: application/json, text/javascript, */*; q=0.01
   Content-Type: application/x-www-form-urlencoded; charset=UTF-8
   X-Requested-With: XMLHttpRequest
   Referer: http://localhost:8090/calendar/mycalendar.action
   Accept-Language: en-EN
   Accept-Encoding: gzip, deflate
   User-Agent: Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.1; WOW64; Trident/6.0)
   Host: localhost
   Content-Length: 110
   DNT: 1
   Proxy-Connection: Keep-Alive
   Pragma: no-cache

Cause

 This issue is due to "Do Not Track" configuration which is configured in Internet explorer which cause "Team Calendars for Confluence" unable to process the request.

Resolution

Disable the "Do Not Track" feature by following the steps below:

1. Navigate to "Internet Option"
2. "Advance"
3. "Security"
4. Disable "Always Send Do Not Track Header"