I have been getting consistent Sync Errors 500 and recently today 503 Errors. I have used OneCalendar (OC) on the following devices using the latest version of OneCalendar on each device. The devices have always been synced to both my Google & Apple iCloud calendars and for the most part have until recently, worked just fine.
• Mac running MacOS 12.2.1
• Mac running MacOSX 10.12.6
• iPad 2020 running iOS 15.3.1 (using Paid version of OC)
• iPad 2019 running iOS 15.3.1 (using Paid version of OC)
• Moto G Fast running Android 11 (Build RPJS31.Q1-53-12-11)
The errors started occurring