Flutter's webview. eye test issue

I am trying to use the visibly exam service using Flutter's webview.
At the following URL, only a black screen appears and nothing is loaded.

This is the webview console error message in this situation.

I/flutter (24422): ConsoleMessage{message: The resource https://d4t7wnutt73jo.cloudfront.net/assets/exam-experience-6105ffcc16d2c9cf77138c6ae816c310f9ea01bc8fe073533a308f433af7afd5.css was preloaded using link preload but not used within a few seconds from the window's load event. Please make sure it has an appropriate as value and it is preloaded intentionally., messageLevel: WARNING}
[AndroidInAppWebViewController] (android) WebView ID 0 calling "onConsoleMessage" using {messageLevel: 2, message: The resource https://d4t7wnutt73jo.cloudfront.net/assets/exam-experience-6105ffcc16d2c9cf77138c6ae816c310f9ea01bc8fe073533a308f433af7afd5.css was preloaded using link preload but not used within a few seconds from the window's load event. Please make sure it has an appropriate as value and it is preloaded intentionally.}
I/AudioTrack(24422): isLongTimeZoreData zoer date time 6 Seconds
I/flutter (24422): ConsoleMessage{message: Failed to execute 'postMessage' on 'DOMWindow': The target origin provided ('https://js.stripe.com') does not match the recipient window's origin ('https://staging.govisibly.com')., messageLevel: WARNING}
[AndroidInAppWebViewController] (android) WebView ID 0 calling "onConsoleMessage" using {messageLevel: 2, message: Failed to execute 'postMessage' on 'DOMWindow': The target origin provided ('https://js.stripe.com') does not match the recipient window's origin ('https://staging.govisibly.com').}

I think it's strange that my mobile app connect to this URL.

govisibly.com/onboarding/intake/exams/{id}/calibration/display

I think this URL is the screen displayed on the PC web.

I hope you help quickly. thank you.