Are all of your directories and files set to 755 and 644 permissions (Linux/Unix only, not Windows)? Which distribution of Linux (or of Unix) or version of Windows is your server? If no, reset to 755/644 (in FileZilla Client, recurse, all dirs or all files).
If above method doesn’t solve the issue, try below code. It worked for me. Continue reading “How to fix – Warning: You do not have permission to modify blah blah blah + Opencart 2”