I have generated a PDF which loads correctly in Firefox, Okular, Evince, iOS Safari, and Adobe Reader, and also validates as PDF/A-3b in multiple PDF validators here and here.
But it does not open in Chrome:
Error
Failed to load PDF document.
I'm aware of previous questions such as Failed to load PDF document in Chrome, but the answers there do not help. This question is therefore not about my specific PDF, but about how to gain further information from Chrome that might help me debug the situation.