I also used Avast and have same problem. But, I'm not unistalled my avast. I tried to allowed apps in Ransomware Shield feature. 1. Open Avast. 2. Open Protection 3. Choose Ransomware Shield 4. Click 'Blocked/allowed apps' 5. Allow An App 6. Add Photoshop from directory C:\Program Files\Adobe\Adobe Photoshop cc 2018\Photoshop.exe Now, my Photoshop can save and my problem solved.
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