This error may be due to your internet connection. Check if it works and try rebooting your router if you're experiencing network issues.
If your internet connection works fine, open Windows Firewall and in "Allow an app or feature through Windows Defender Firewall", click on Change settings, then add Outlook in the allowed apps list.
Try increasing the server timeouts setting in Outlook by going to File > Account Settings > Account Settings. Select your email account and click More Settings. In the Advanced tab, under "Server Timeouts", drag the slider to the right and save the changes.
If you still get this error, try starting Outlook in safe mode. Press the Windows + R keys, next type Outlook.exe /safe in the field and click Ok.
This error 0x800ccc0f generally occurs where you are either sending or receiving emails through Outlook.
Cause of this error: The network firewall is stopping a connection between Outlook and the Mail Server.
1: Disable the Antivirus and Firewall.
2. Run ScanPST.exe or ScanOST.exe (Inbox Repair Tool)
3. Quick fix through the third party tool (PST repair tool)
4. Check Outlook Profile Settings
5. Clear up Suspicious Emails from Outlook
6. Start MS Outlook in Safe Mode
If after following all the methods you are still facing an error, then it's important to convert your OST file to PST and then repair your Outlook PST file using a third-party tool.
Also, PST repair software will help you get all your data back in the same format as it was before the error.