Code:
5/05/2017 - mIRC v7.49

Changes:
1.Changed CAP invite-notify support so that invite notifications are now displayed by default.


It would seem that Khaled added CAP support for invite notifications, but perhaps did not [yet] add readiness for this behavior to trigger the On Invite event.

Reasonably, invite notifications do not trigger the On Invite event, because most scripts are used to that event only firing for invites directed at the user and not a third party. I don't know what a good proposal is.

Maybe Khaled can figure out a way to let the RAW event handle all events, even if they're already bound to an On Event handler. Thereby RAW INVITE would handle all invite notifications that On INVITE do not.

In the mean time, you can use On PARSELINE as previously suggested.

Well. At least I won lunch.
Good philosophy, see good in bad, I like!