Hi @michael.schmid,
Thanks for reaching out!
The error you get refers to the fact that this field is mandatory to be filled. Here:
You can also find it in Google Api Docs. So, you need to fill out the attendee_email field.
In case any additional questions will appear, please let me know.
Best,
Gulce
@Gulce thanks for your answer. But as far as I can see in the Google doc, the attendee_email field is not mandatory as I am not adding an attendee (same with creating a new event where I don’t add an attendee email as well and it works just fine)
I just tried it with the same data on the Google API page and left the attendee_email empty and it worked just fine. The only mandatory field I had to fill for the update event action was cal_id, event_id, datetime start and datetime end.
Can you please check again on the plugin side?
Hi @michael.schmid,
I’ve passed this to the developer team, and I’ll get back to you once I have any news.
In case you have any other questions, please let me know.
Thank you for understanding. 
Best,
Gulce
Hi @michael.schmid,
We’ve updated the plugin and added a new call without the attendee_email field. Here:
Kindly ask you to upgrade your plugin to the latest version (1.37.0) and give it a try. Thank you so much for your patience!
Let me know if there’s anything else I can help you with.
Best,
Gulce
Thanks for the quick support, it is working perfectly now 
Always welcome! @michael.schmid
Please feel free to reach us any time you have any questions. 
Best,
Gulce.
