@Just_me - I found the Chrome extension "Malwarebytes Browser Guard" to be interfering--as soon as I disabled it, everything worked like a charm.

I was able to get QBO to work perfectly in Incognito Mode though. If you are still having troubles in Incognito Mode, either there's a browser extension interfering (that has "Allow Incognito Mode" checked) or there's a deeper problem, but that's what corrected my issue.