Hello akonovalenko
Fusion 360 api used chrome to render the palettes, but soon it will not be supported. I suppose you were not using the new web browser. Take a look at the palettes()->add() function declaration:
/// Creates a new Palette.
/// id : The unique id for this palette. The id must be unique with respect to all of the palettes.
/// name : The displayed name of this palette. This is the name visible in the user interface.
/// htmlFileURL : Specifies the url to the HTML file that will be displayed in the pallete. This can be a local file or on the web.
/// isVisible : Specifies if the palette is initially visible or not. It's useful to create it invisisibly, change other desired
/// properties and then use the isVisible property to finally make it visible to the user.
/// showCloseButton : Specifies if a "Close" button should be displayed on the palette to allow the user to easily close it.
/// isResizable : Specifies if the palette can be resized by the user or not.
/// width : Specifies the width of the palette in pixels. If no width is specified a default width will be used.
/// height : Specifies the height of the palette in pixels. If no height is specified a default height will be used.
/// useNewWebBrowser : Specifies true to use new browser in the palette. This is false by default to support existing clients.
/// Support for old browser is deprecated and will be taken out soon.
/// Returns the newly created palette or null in the case the creation failed.
Ptr add(const std::string& id, const std::string& name, const std::string& htmlFileURL, bool isVisible, bool showCloseButton, bool isResizable, int width = 200, int height = 200, bool useNewWebBrowser = false);
I got same results as yours at browser-info.net when useNewWebBrowser == false, but the browser is not identified when useNewWebBrowser == true

