Good day, everyone...
I found just a tip, and maybe it's related. Under "configuration", having "Advanced" enabled, the first tab called "Component", there is a mark called Category separator, which present a "|". The tooltip says that, if a 400 error occurred, I should change the "|" for a comma ",". I did it and... same issue.
I have another question with my issue: How does JEvents determine which users appears at the dropdown selector of users? First I thought that only Managers, Administrators or Superusers (from Joomla groups), but now I see a bunch of users that doesn't have those privileges. Maybe it is related, maybe not, but I consider important to comment it in here. My users are members only from Administrator group, and two Superusers. It only work for the Superusers guys.
So far, no luck yet.
Greetings.
JC