Oxygen not recognizing tag template

I’m trying to make a template for tag pages but I can’t get Oxygen to recognize it. I’m just getting into templates so there’s probably something obvious I’m missing.

I made a child theme from Oxygen for my site. I made a copy of archive.php, changed the name to tag.php, added some code like <?php echo 'is this working?'; ?>, and put it in the child theme directory. If I go into the editor in WordPress and select my child theme, I can see tag.php. Also, the permission for the file is 644 and for the directory it’s 755. I’ve got regular posts and custom type posts, but it doesn’t work with either. If I edit archive.php, then the changes will show up on the tag pages. I tried to make a category.php file as well and that didn’t work either, but I have some templates like single-mycustomposttype.php and those work. What am I doing wrong here?