Chrome javascript debugger breakpoints are not working

Whether I set breakpoints directly on the source/console or add a debugger on my code, the browser doesn't seem to respond to them. Any ideas why? Here's my code:

 if (select[i].placeholder != undefined && select[i].placeholder != '' ) {
        selected.appendChild(document.createTextNode(select[i].placeholder)); debugger;
    } else if (select[i].options[0].value == '' && select[i].options[0].textContent != '' ) {
        selected.appendChild(document.createTextNode(select[i].placeholder));
    } else {
        selected.appendChild(document.createTextNode('Select an option'));
    }

In Dev Tools, on the Sources panel, there's a button that looks like a breakpoint marker with a line through it: That button disables all breakpoints. To re-enable them, click the button.

Here's what it looks like when they are currently enabled (clicking it disables them):

...and when they are currently disabled (clicking it enables them):