How do you reset the preferences if you can't open Photoshop? Is there another way?
Yes, you can manually delete the preferences file.
First, quit Photoshop!
Then navigate to:
~/Users/[Username]/Library/Preferences/Adobe Photoshop CC 2018 Settings
and delete the Adobe Photoshop CC 2018 Prefs.psp file
C:\Users\[username]\AppData\Roaming\Adobe\Adobe Photoshop CC 2018\Adobe Photoshop CC 2018 Settings
and Delete the Adobe photoshp CCx Prefs.psp and Adobe Photoshp X64 CCx Prefs.sps files
If deleting the prefs.sps file doesn't solve the issue . . .
When you uninstalled and reinstalled, did you try using the CC Cleaner tool? Using that tool you would still uninstall and reinstall but sometimes the process is more successful with the Cleaner tool.
Fastest solution for me is to open the file with a program called PAINT and simply hit SAVE. It will then open in Photoshop.
i don't have a prefs.psp or prefs.sps file in that directory. now what?