Wildcard argument to cygwin utility

Try using your ls command without the double quotes, like:

ls myfolder/*.csv

Because you put the double quotes around the wildcard (asterisk), the shell doesn't do any expansion and will try to find a file named *.csv.

mtak@frisbee:~$ ls tst/*.txt
tst/bar.txt  tst/bla.txt  tst/foo.txt
mtak@frisbee:~$ ls "tst/*.txt"
ls: cannot access tst/*.txt: No such file or directory