FTP error 530 Login incorrect

First of all check which FTP is using the Cpanel proftpd or pureftpd

If it is using the proftpd, do the folowing to fix the 530 error
1. First of all try the /scripts/ftpupdate
2. grep /etc/proftpd/passwd.vhosts (here is the domain username)
3. If it is not present there then grep /etc/proftpd/
4. Check details and cat >> /etc/proftpd/passwd.vhosts
5. Paste the main ftp account details in this file
6. /scripts/restartsrv_ftpserver

Note: please be careful in doing it. If you have specified cat > /etc/proftpd/passwd.vhosts, it w
ill overwrite the whole content.

If it is pureftpd:
Do the above 6 steps
7. Sometimes you need to rum "/usr/sbin/pure-uploadscript -B -r /usr/local/bin/ftpfilter" also