Warning: Cannot modify header information – headers already sent by
Please check the following that might be help you to get this resolve
1. Remove Extra spaces or lines before <?php or after a closing?> php tag
2. Check Unparsed HTML before the Header.If exist then remove it.
3. Body content sent before the Header.
4. Incorrect PHP Encoding Format.
Fix #1: Upload a Fresh Copy
Upload a Fresh Copy via Cpanel/FTP.If it’s a regular plugin or theme file, you can uninstall and reinstall it.
Fix #2: Edit the Trouble File
If you identified the Trouble File, you can download the file from FTP, or you can edit it directly in cPanel.