SteamHTMLSurface Callback<HTML_StartRequest_t> is not being triggered

[Rosslington]

When trying to use the the HTML_StartRequest_t callback after using LoadURL, the callback is not getting triggered.

Steamworks.NET Version: 2025.162.1
Platform: macOS Tahoe (26.0.1)
Unity Version: 6000.2.6fa (Intel)

Context:
I've created a SteamManger based on the example in the Steamworks.NET docs, that loads the Steam SDK fine and I can load my Steam user details. Once this is all initialised, I then enable a SteamHTMLManager object that initialises a Steam HTML Surface and renders it to a UI Image texture. Rendering the HTML Surface is all working fine, it's just this specific callback that doesn't seem to work.

Other callbacks such as HTML_FinishedRequest_t and HTML_URLChanged_t work fine.

Example Code:

private CallResult<HTML_BrowserReady_t> OnHTML_BrowserReadyCallResult;
    private Callback<HTML_NeedsPaint_t> m_HTMLNeedsPaint;
    private Callback<HTML_StartRequest_t> m_HTMLStartRequest;
    private Callback<HTML_FinishedRequest_t> m_HTMLFinishedRequest;
    private Callback<HTML_URLChanged_t> m_HTMLURLChanged;


...
// Once the Surface has initiatialsed

        m_HTMLStartRequest = Callback<HTML_StartRequest_t>.Create(OnHTML_StartRequest);

...

    void OnHTML_StartRequest(HTML_StartRequest_t pCallback) {
        Debug.Log($"[SteamHTMLManager] StartRequest: URL: {pCallback.pchURL}");
        SteamHTMLSurface.AllowStartRequest(pCallback.unBrowserHandle, true);
    }