What have you done for trouble-shooting so far?
Restoring Preferences after making sure all customized presets like Actions, Patterns, Brushes etc. have been saved might be a good starting point:
Please read this (in particular the section titled "Supply pertinent information for quicker answers"):
I uninstalled PS CC 18' and reinstalled it again. Still didnt work. Then I increased the space allocated for PS to use to 13245 MB. Still didnt work. But I didnt try restoring preferences. Thanks I'll try that next.
So I downloaded Photoshop CC 2015.5 and it worked fine. So I still don't know what was wrong with Photoshop CC 2018. Thanks for all your help though. Happy Holidays to you.
So restoring the Preferences did not make a difference in CC2018?
Happy Holidays to you, too!