I believe I have finally found the solution to this. Over the past couple years, I've had this behaviour occur now and then, usually after something updates (not sure what... probably Windows updates). Usually I'm able to get HTTPS working again by removing/installing new Fiddler certs multiple times, but I was never able to create reproducible steps to fix it.
I ran into the issue again yesterday and no matter what I did, I kept getting the NET::ERR_CERT_AUTHORITY_INVALID error as I did in the original post.
This morning I tried the following and it worked:
1. Fiddler Options / HTTPS / Disable 'Decrypt HTTPS traffic'
2. Fiddler Options / HTTPS / Actions / 'Remove Interception Certificate'
3. Reboot PC
4. Open command prompt with admin privileges and run: certutil -urlcache * delete (this will clear the Windows cert cache)
5. Reboot PC
6. Open Fiddler and re-enable 'Decrypt HTTPS traffic' -> Follow prompts to install cert
7. Reboot PC
8. Open Chrome, Open Fiddler, Profit!