Could not resolve host: magento-community; Host not found

"Could not resolve host: magento-community; Host not found" error in Magento usually occurs when the Magento installation is unable to connect to the Magento repository to download and install extensions. Here are some steps you can follow to fix this error:

1. Check your internet connection - Ensure that you have a stable internet connection and that there are no network issues that may be preventing Magento from connecting to the Magento repository.
2. Verify the Magento repository URL - Verify that the Magento repository URL is correct and properly configured. To do this, navigate to System -> Web Setup Wizard -> System Configuration -> Magento Marketplace and ensure that the Magento repository URL is set correctly.
3. Check firewall settings - Ensure that your server firewall is not blocking the connection to the Magento repository. You may need to whitelist the Magento repository domain name or IP address in your firewall settings.
4. Clear Magento cache - Clear the Magento cache by navigating to System -> Cache Management and clicking on the "Flush Magento Cache" button.
5. Manually install extensions - If the error persists, you can try manually downloading and installing the extension from the Magento marketplace website.

If none of the above steps work, it may be best to seek the assistance of a Magento developer or support team who can help you diagnose and fix the issue.