Why can't I use FTP with new version 12?

I do not have any problem using FTP with version 11.
Now, after updating to version 12 Pro, every time I clicked on the saved FTP link, it keeps asking for password, and even after I put the correct password in, it asks again and again. Very frustrating.
I have no problem using the same user name and password with the CPanel.
What do I have to do now to get it working?

What does the FTP log show?

Could your firewall software be treating the old and new versions differently?

The FAQ on FTP problems discusses both in more detail, as well as some other possibilities.