All notes from Calendar are missing

[Tars]

All notes from the calendar are missing. The box is empty, I've checked. What are the options for solving this problem? 

[MrGhoul · Accepted solution]

Ensure that the calendar sync feature is enabled on your device.
Go to Settings > Accounts and backup > Manage accounts.Select your account and make sure Auto sync (calendar) is turned on.

Check for deleted notes in your calendar by going into calendar settings or any associated note-taking app and selecting trash, then restoring the notes.

Also, ensure airplane mode is turned off in your quick panel

[Tars]

Thank you so much for your prompt response. I checked your recommendations again. until I can't stop all the notes in the calendar.

[MrGhoul]

You are welcome!
If you found my response helpful, could you please tap the 3 dots next to my original post and accept it as a "solution". This will help other users to resolve the same problem/issue . Thank you!