If anyone has done it or any idea on how to do it, please help.

I am trying to build calendar feed/subscription from an existing Spring Boot (Java 17) application. I got to the part to build an URL ending with .ics and it’s able to work for Google but not in Outlook. (Getting Error 28).

I’ve tried searching for this Error 28 but no help so far.

For example the below URL which is outputting simple ICS file works perfectly with all calendars but mine not.

https://ics.calendarlabs.com/35/ba78f991/Australia_Holidays.ics

Header from calendarlabs.com

Header from my app

I am not sure what am I missing to get it to work perfectly. I would really appreciate any help with above.