Reset your Photoshop preferences, which you can find under the General tab in Photoshop preferences.
I have followed your suggestion and on the Photoshop general preferences I have clicked on the button "Reset preferences on quit" . . . . . . . . but it did not fix the problem .
Do you have another suggestion?
Thank You, P
Try unticking Use Graphics Processor under the Performance tab in Photoshop preferences.
If that doesn't work uninstall Photoshop using the drop-down menu in the Creative Cloud app (see screen shot) then reinstall it. If that doesn't work, uninstall again and run Adobe Cleaner Use the Creative Cloud Cleaner Tool to solve installation problems before reinstalling.