Dear Ferd II,
Thanks for the quick reply.
First, if I do what you suggest (go to iCloud: Report junk Calendar invitations), there are two problems:
1. There is no Report Junk button or menu.
2. Accessing the calendar thru the iCloud webpage does not show other calendars (e.g. Gmail), in other words I do not see any of the spam invites this way, thus there is nothing to select and delete...
Second, if I do what is suggested at the end of the thread I referred to above (here it is again: https://discussions.apple.com/thread/6508265?start=30&tstart=0), following the instructions in the three nice and clear screenshots, I run into the following problems:
1. When I try to clickNhold one such repeating spam invitation in order to dragNdrop it into a newly created Spam folder, I cannot do it, the item does not move, it cannot be dragged!
2. When I try to delete the newly created Spam folder (but with none of the spam in it, since I couldn't drag any of it there), I do NOT get the window with the choice "Delete and Don't Notify", the only choice is Delete or Cancel. In other words I do not know if such a deletion will or will not send a message back to the spammer.
Here are a couple of other things that may help someone help me to solve this problem:
All these repeating spam invitations are GREYED OUT. Is this a way for the spammers to make it more difficult to deal with them?
If I disable the gmail calendar within the Apple Calendar app (either on the Mac or the ipad), all the spam disappears (this would be a nice and easy solution, except that this doesn't delete them, they are only not displayed I think). The problem with this is that all the non-spam events disappear as well, which is unacceptable because we have been using the gmail calendar as our main calendar with all the important events in our lives.
Finally, all 4 repeating spam invitations started in October and November 2017, and it looks like we succeeded in stopping new ones to come in, in other words no new spam since mid November. So the problem is
1. how to delete them without notifying the spammers? and
2. how to delete notifications that repeat infinitely into the future? (Nine per week! 👹) and
3. what's up with greyed out items and how to delete them?
To avoid any further misunderstanding: we do *not* use the Gmail app or the Google calendar app on any of our iDevices and we do *not* use the Mail application on the Mac. But we DO use the Mail app on the iDevices to access our gmail account, and we see and access all our gmail calendar events, including these spam invitations, only within the Apple calendar app.