Since you tried all you found on the Internet I can't offer new ideas but will share the usual.
Most of the time I just install another photo viewer (mostly from Ninite.com) and try those. But this is also an issue with backups. We only lose what we don't back up and with RANSOMWARE being a problem sometimes folk get hit with that and the files are gone unless they had backup copies.
Some (a lot) of my photos will no longer open. I have tried everything I have been able to find on the internet with no luck. I think it started when I upgraded to windows 10, but not sure. I have a folder named Mom & Dad with 971 files on April 10th 2019 I moved all of the pictures that would not open to a new folder I named files that won't open, 197 total. Today I checked to see if any of them would open, they won't. I also checked to see if there were any in the Mom & Dad folder that would open then, but not today April 23 and I found 4 files, 2 jpeg, 1 bmp, 1 png. This just keep happening and I have no ideal what to do please help, I love my photos and it is breaking my heart.