By default CrazyTalk 8 doesn't support 4K or other Ultra HD screens. However, you may find the issue can be resolved using the workaround below (Windows version).
1. Right-click on the CrazyTalk 8 desktop icon and select Properties.
2. On the Properties dialog box, select the Compatibility tab. Now click "Change high DPI settings".
3. On the second dialog box, go to "High DPI scaling override".
4. Check "Override high DPI scaling behavior...", and from the drop-down select "System (Enhanced)".
5. Click OK, and then OK again.