Symptoms
Mouse cursor does not automatically get captured when moving over Virtual Machine window.Cause
One of the probable reasons for this problem is that the Smart Mouse option is not enabled. It is the very feature that determines, whether mouse pointer is hovering over Virtual Machine window and automatically switches, if necessary, the area of its operation.Resolution
1. Shut down virtual machine if it is currently running.2. Click on Virtual Machine in Mac menu bar > Configure... > Options > Advanced tab > Enable "Smart mouse"
3. Click OK and start virtual machine and check if the issue persists.

If the issue persists then follow the below mentioned steps.
1. Please update Parallels Desktop to the latest build:
1.1. Go to Parallels Desktop in menu, click Check for Updates...
2. Launch the Virtual Machine and go to Start > Control Panel > Add or Remove programs and remove Parallels Tools,
3. Restart the Virtual Machine,
4. Install Parallels Tools by clicking Virtual Machine menu > Install Parallels Tools.
No
Yes