GPTZero become useless?

I have been using GPTZero for a few months and I noticed a very weird thing - now it marks almost everything as AI!!! I use it sporadically, incognito window, one-off text analysis. I started to get suspicious a week ago - basically I just sometimes dump fishy text there to see how bad text should I expect.

Now here comes the twist: I am not a native speaker, and in the past I did a "control test" with GPT Zero with texts from my own publications. All marked as high confidence human. But now these are also marked as AI!!!

Anyone experienced similar? Is it just the marketing, and if I start paying eventually I get good results? (I tried their paid tier in the past, but I do not get very far with their basic sub...)