QWebEngineView window is blank and non-responsive upon launching

Trying to incorporate a web view into my PyQt5 application, but can’t even get simple demo case to launch properly. Running browser.py included with the book, or the sample application on this page in the tutorial, launches an empty widget window with the proper title, but it’s blank (same result if I launch from Spyder or on command line). After a few seconds I get the blue spinning icon and window title says it’s not responding. I’m running Windows 10, with Python 3.8.5, and PyQt 5.9.2. I’m guessing it’s something with my environment rather than the code, given straight up simple examples won’t run, but I’m not even sure where to start looking. Any tips appreciated!

EDIT: Forgot to mention, when I kill the hung window, I get the following error message at the command prompt, in case it helps:
[28852:19036:1216/153956.572:ERROR:broker_win.cc(59)] Error reading broker pipe: The pipe has been ended. (0x6D)