Why iCloud calendar stop syncing despite following all the syncing instructions?

Please follow the steps below to resolve this issue and re-sync an affected iCloud calendar:

(1) Open the calendar app.

(2) Select the calendar you are having trouble syncing & turn off public calendar for all iCloud calendars and tap done in the top right corner.

Select the calendar you are having trouble syncing & turn off public calendar for all iCloud calendars and tap done in the top right corner.

(3) Navigate to the Settings app on your iPhone.

(4) Tap on your name to enter your iCloud settings.

(5) Tap on iCloud again.

(6) Turn off calendar in iCloud settings & Keep the calendar data on the iPhone.

(7) Once the setting is completely turned off, Close the calendar app by switching into multi-tasking view and swiping the calendar app upwards.

(9) Once you have waited 10 minutes, Turn on public calendar for the affected calendars and attempt to re-sync it back to the Ecalendar with the calendar URL.

(10) Open the Ecalendar mobile app after copying the URL.

(11) tap on your calendar name and tap on the 2 arrows chasing each other in the bottom right corner.

(12) Before we continue and sync the calendar we must remove the problematic calendars that were previously synced. Tap on Edit in the top right corner and remove the iCloud calendars that are not updating properly.

(13) Once removed tap Sync a different calendar and then calendar URL to paste the URL you copied previously.