I did remember a while back Preview would open my files instead of Photoshop, and the problem was in Firefox's sandbox settings. I had to dial it down to 2. That's the only time I remember this happening.
https://community.adobe.com/t5/photoshop-ecosystem-discussions/can-t-make-adobe-photoshop-cc-2018-default-application-in-macos-sierra/m-p/9447445
This is the workaround. It's fixed it for me and others using earlier versions of OSX:
"For a workaround, browsing to about:config and setting "security.sandbox.content.level" to 2 (instead of the current default value of 3) and then restarting your browser may work. This makes the security sandbox more permissive, but doesn't completely disable it. I haven't reproduced the problem so I can't confirm if this works around the problem or not. I've tried on 10.13 and will test on some other versions."
This has nothing to so with the Adobe PSD problem, this is where Photoshop is removed as an association for image files in OSX.
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