Andrea Vahl said
10 months, 2 weeks ago: @bertievg @zoejones From what I’ve seen this is a mistake although I’ve heard from someone who thinks it’s an evil conspiracy from Facebook 
I also received this message on one of my pages but the Page is still categorized as a Product and I still have control over the category. I just ended up x-ing out the message and I haven’t seen it since. Facebook supposedly gives you a link to the help area where you can report it as not being a community page but it doesn’t go to a place where I see that you can report it.
Just make sure your page is still categorized as you want in your Info area (Edit Page, Update Info, and then look at the category).