Some start_url links suddenly require login ("hosted by another user")

API and Webhooks Meetings
1

We are using Zoom ISV with service accounts and dummy users.
Normally, anyone who opens the start_url becomes the host without logging in.
This has been working correctly for years.
Starting from early December 2025, we found that some start_url links
(around 30 meetings) suddenly stopped working. When opening the start_url,
Zoom shows this error:
“You cannot start the meeting because it is hosted by another user.”
Other start_url links generated the same day still work properly.
This means the problem is not on our system side — it seems certain ZAK
tokens generated via API were invalidated or rejected by Zoom backend.
We suspect an internal issue with ZAK validation for ISV.
Example problematic meeting ID:- 86580082526
We can provide the full start_url privately via DM.

Please help investigate why only some ZAK-based start_url links were rejected.
This issue affects our production system and customers cannot start meetings.
Thank you.

2

Hi @Public_Connect
Thanks for reaching out to us and welcome to the Zoom Developer Forum.
Sorry for the late reply here.
Can you please confirm if you are still experiencing this issue on your end?
If so, I will follow up with a DM for more informatino about your account

3

The above issue is still occurring. I would like to understand the exact cause of this problem; however, I have not yet received any response or explanation from any party. Previously, I contacted and discussed this matter with Zoom, but I have not received a concrete answer.

4

Thanks for the update here. Can you please open up a support ticket here so they can help you look further into this issue: