Thank you for the report. I'm not seeing this behavior in our pre-public build or my installation running 16.1.6425. The Save and Cancel buttons both enable as expected when a change is made. Perhaps there is a required setting not configured on that page? Try this: Click on the first setting on the page, POP Banner, and then use your Tab key to tab through all the settings on the page. Look for any red validation errors that might appear. If you do see an error, configure that setting and you should hopefully be able to save.
Please let me know what you find! If you're still seeing this issue, please let me know the browser you're using as well.