chown won't change ownership
Solution 1:
On the one hand:
chown with a simple user parameter, not including the separator : (or obsolete .) changes the user ownership of further given file(s) and leaves the group ownership of the file(s) unchanged.
On the other hand:
ls -halg displays only the group ownership of a file in its output because of the included option -g.
Thus changing only the user, which worked (no error was displayed) didn't change the result of ls -halg. ls -hal should have been used here to see the change.