Thanks for letting us know Toby, I was just going to refer you to the article I wrote last week.
Yep, Google has been spewing warnings for about a year if you ever inspected your console. Your old site is grandfathered in. Lance had prepared for this event by adding an area in the back end of SLP where you add your API key. Other WP Locator Plugins did not plan for that event and are having their customers change snippets of lines of code.