I had a chat session with Apple Support about exactly this problem - they solved it.
The tick is to make sure that the "default" on both sides is "Calendar" rather than "Work", "Home" or something else.
Here is the transcript:
Wednesday, Nov 16, 2016 01:37 PM
Duration 36 minutes 11 seconds
Nicole
Thanks for contacting Apple Support. My name is Nicole. Please give me a moment to look over your information.
Nicole
Hi Claus! How are you?
cl#####@gmail.com
Having trouble synching my calendar between MAC and iPAD via iCloud. Used to work, but not anymore - probably when I installed one of the last OS upgrades. Tried closing iCloud on both sides and then re-opening, no help.
Nicole
I can understand how that would be a cause for concern!
Nicole
To make sure I am clear on the issue, your Calendars are not syncing between your Mac and iPad using iCloud?
cl#####@gmail.com
Correct..
Nicole
I know it can be disappointing to not have your Calendar syncing. I will be happy to work with you to determine the best resolution, OK?
cl#####@gmail.com
Great..
Nicole
To start, may I ask the OS X version the Mac is currently using?
Nicole
You can find the OS X by clicking on the Apple in the upper left corner and select ‘About This Mac.’ It will appear as 10.x.x.
cl#####@gmail.com
10.12.1
Nicole
OK, thank you!
Nicole
Can you tell me the iOS version your iPad is using? This can be found by going to Settings, then General and select About. The iOS will be listed beside ‘Version’.
cl#####@gmail.com
9.3.5
Nicole
OK Claus, can you tell me which iPad you have, we may need to update it so your iPad is up to date as well.
cl#####@gmail.com
iPad 2
cl#####@gmail.com
16GB
Nicole
To confirm, is it an iPad Air 2 or an iPad 2?
cl#####@gmail.com
iPad 2 (Model: MC769LL/A)
Nicole
OK Claus, we can explore a few other things.
Nicole
Can you verify that both devices are signed in with the same Apple ID?
Nicole
Are you familiar with how to do so?
cl#####@gmail.com
Confirmed - I only have one AppleID
cl#####@gmail.com
tell be how to verify...
Nicole
OK, on the phone, please go to Settings>iCloud.
Nicole
I apologize, I meant iPad.
cl#####@gmail.com
OK, I'm there
Nicole
Good, can you tell me if it shows your Apple ID at the top?
cl#####@gmail.com
Yes, it does
Nicole
Awesome!
Nicole
Now in the list of items showing, do you see Calendar?
cl#####@gmail.com
By the way, when i got to the WEB site to manage my AppleID, is shows both devices...
Nicole
Great! Thank you for letting me know!
cl#####@gmail.com
Yes, and it is "ON"
Nicole
Good!
Nicole
Now what we will do is to go into your Calendar settings to confirm it is the default calendar.
Nicole
Have you accessed your calendar settings from the iPad before?
cl#####@gmail.com
No
Nicole
No worries!
Nicole
I will help you find it. Please go to Settings>Mail, Contacts, and Calendars.
cl#####@gmail.com
OK, got it
Nicole
Good! Now do you see ‘Accounts’?
cl#####@gmail.com
Yes.. iCloud, Hotmail, Gmail
Nicole
OK, do you see the Calendar section?
cl#####@gmail.com
Yes
Nicole
You may need to scroll down a bit.
Nicole
OK, now in the section that says ‘Default Calendar,’ what does it show?
cl#####@gmail.com
Default calendar is "Home"
Nicole
OK, good it sounds like everything is as it should be there.
Nicole
Now lets take a look at your Mac’s settings.
Nicole
Please go to the Apple in the upper left corner and choose System Preferences.
Nicole
Here you should be able to view your iCloud account to make sure it is signed in.
cl#####@gmail.com
It has a Checkmark...
Nicole
Good!
Nicole
Now, please open your Calendar application on the Mac and choose Preferences from the drop down.
cl#####@gmail.com
OK,
Nicole
Now, do you see the Default option on the General tab?
cl#####@gmail.com
Yes it is "Calendar"
Nicole
OK, since the the calendar on your phone indicates ‘Home’ as the default, this is where the conflict may be.
Nicole
Which device do you typically use to add events?
cl#####@gmail.com
MAC
Nicole
OK, so what we can do is change the default on the iPad to “Calendar”, instead of “Home” on the iPad.
cl#####@gmail.com
OK, I switched to "Calendar" as default on iPad/iCloud...
Nicole
OK, gerat!
Nicole
Let’s go ahead and take a look at your iPad and see if your events are appearing.
cl#####@gmail.com
Bingo! Thanks.
Nicole
Awesome!
cl#####@gmail.com
You guys are tops! Thanks
Nicole
It has been a pleasure working with you today! Before we end the chat I want to confirm you are 100% satisfied with the resolution path we have set for you by changing your default calendar settings. Is there anything additional I may do to ensure you are satisfied?
cl#####@gmail.com
Note: In some of the Apple Forums, others are describing same problem - you might want to publish this there...
cl#####@gmail.com
I'm good. Thanks
Nicole
That would be a great idea! Did you know you can post items there as well?
cl#####@gmail.com
No, I did not know...
Nicole
Yes, that is what make the forum such a useful tool. All Apple helping other Apple makes delicious Apple pie!
Nicole
I am going to send you an email really quick with some articles relating to the resolution we set on today. The email will also include your case number, just in case you need to contact us again! Would the email address provided be the best one to use?
cl#####@gmail.com
Yes, Thanks
Nicole
Great!
Nicole
Thank you for being the best part of Apple! If there is nothing further, I will close the chat window so you may request a transcript of our chat! Also keep in mind that support.apple.com is a great resource for all things Apple! Have an Appletastic Day!
cl#####@gmail.com
You too!
Nicole
Again, my name is Nicole and it has been a pleasure working with you today. Please be aware that any comments you are asked to submit after our chat will only pertain to the service of the Advisor named in the request, and not about your device itself. Thank you again!
Nicole
May I go ahead and end the chat?
cl#####@gmail.com
yes, bye
Nicole
Bye! Bye!
Sincerely,
Apple Support
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