If you facing any accessible issue towards the Website, CPanel, and Webmail, probably the IP address already been blocked in the firewall.
You may be able to quickly resolve the issue yourself if you have access to WebHost Manager and the ConfigServer Firewall (CSF).
How to Access ConfigServer Security & Firewall (CSF)
1. Login to your WHM Dashboard for your server
2. Under Plugins choose ConfigServer Security & Firewall.
Unlocking an IP Address in CSF
1. From the Firewall management page, you will want to scroll down to Search for IP, it should look similar to the following:
2. In the empty text input, paste your IP address of the computer that has been blocked and clicked the button.
You may find the public IP address of your local computer by can search ‘IP‘ on Google and it will show you your IP address or alternatively access this https://whatsmyip.com/ may work as well.
3. The report will show you if there are any Permanent or Temporary Allows or Blocks on the IP address.
If the IP address is blocked, the reason for the block will be listed and there will be a button towards the bottom of the Report to Unblock the IP address.
Clicking on this will Unblock the IP address:
Allowing (Whitelisting) an IP Address in CSF
1. Using the Steps above, navigate through to the Firewall Management page and search for Quick Allow option.
2. Enter in the IP address that you would like to add the Allow for into the Green Input box, along with an optional comment for the allow (such as “Office network”), and click the Quick Allow button.
This will add the Allow for the IP address and should be effective immediately.
This rule will remain in place until explicitly removed.