Improper handling of zero length matches

OS: Mac OS Monterey 12.4
NotepadNext: Qt version 5.15.2.

When i using the "find" function in "regular expression" mode, i can not find anything.

There is some words like this:
aaaaaa
bbbbbb
ccccccc
I want to add the "," to the end for each line.
In "Notepad++" i can use the "$" to find it , and use the "," to replace.
but a single "$" is not work in notepadnext.