Hi
I assume you can't access the Photoshop interface, if so there's another way to reset the preferences, go to this location
C:\Users\You User Name\AppData\Roaming\Adobe\Adobe Photoshop CC 2018\Adobe Photoshop CC 2018 Settings
Then delete the Adobe Photoshop CC 2018 Prefs.psp
You my need to enable hidden items to view the files
If that doesn't work try reinstalling Photoshop using the Adobe cleaner tool
Use the Creative Cloud Cleaner Tool to solve installation problems
Edit: forgot the mention make sure you end Photoshop.exe task in task manager before deleting the preference file