I faced same issue where waiting room is not enabled. I doubt that webhook is also not triggering for this case. Please let us know in which case this can be happen. See response of blow API call, where participant Amit Tambe has same issue.
GET https://api.zoom.us/v2/report/meetings/88144796135/participants?page_size=30
{
“next_page_token”: “”,
“page_count”: 1,
“page_size”: 30,
“participants”: [
{
“attentiveness_score”: “”,
“duration”: 1391,
“id”: “null”,
“join_time”: “2020-11-17T17:01:56Z”,
“leave_time”: “2020-11-17T17:25:07Z”,
“name”: “Dipen Sompura@270”,
“user_email”: “dipen.sompura+2@edutinker.com”,
“user_id”: “16778240”
},
{
“attentiveness_score”: “”,
“duration”: 1348,
“id”: “SW7FTaw7TjaaenC2hTGeyA”,
“join_time”: “2020-11-17T17:02:39Z”,
“leave_time”: “2020-11-17T17:25:07Z”,
“name”: “Nilesh Gupta@272”,
“user_email”: “”,
“user_id”: “33555456”
},
{
“attentiveness_score”: “”,
“duration”: 1332,
“id”: “c6rShWqxSb2eXOg9xpUZcg”,
“join_time”: “2020-11-17T17:02:55Z”,
“leave_time”: “2020-11-17T17:25:07Z”,
“name”: “Akash Aggarwal@273”,
“user_email”: “”,
“user_id”: “50332672”
},
{
“attentiveness_score”: “”,
“duration”: 998,
“id”: “lLxPvLW0TYSMS5If4W1PUw”,
“join_time”: “2020-11-17T17:03:17Z”,
“leave_time”: “2020-11-17T17:19:55Z”,
“name”: “Amit Tambe@274”,
“user_email”: “”,
“user_id”: “67109888”
},
{
“attentiveness_score”: “”,
“duration”: 313,
“id”: “lLxPvLW0TYSMS5If4W1PUw”,
“join_time”: “2020-11-17T17:19:55Z”,
“leave_time”: “2020-11-17T17:25:08Z”,
“name”: “Amit Tambe@274”,
“user_email”: “”,
“user_id”: “67110912”
},
{
“attentiveness_score”: “”,
“duration”: 1266,
“id”: “bWaHHuHsTamo4zTzRTpOiw”,
“join_time”: “2020-11-17T17:04:01Z”,
“leave_time”: “2020-11-17T17:25:07Z”,
“name”: “Narendra Zatakiya@271”,
“user_email”: “”,
“user_id”: “83887104”
}
],
“total_records”: 6
}