When trying to connect to a remote computer using Parallels Access, you get the error:
Unable to connect to computer
Disable Firewall and Anti-Virus software.
Make sure that Support for assistive devices is turned on:
In OS Maverick or earlier: Apple logo > System Preferences > Accessibility > Enable access for assistive devices.
In Yosemite OS / El Capitan: Apple logo > System Preferences > Security & Privacy > Privacy > add Parallels Access to the list of application Allow the apps below to control your computer)
Please check whether Parallels Access is in Accessibility list:
Open System Preferences > Security & Privacy > Privacy > Accessibility
If there is no Parallels Access icon, drag and drop it from Applications. Then check the checkbox to allow Parallels Access control.
Please make sure the following network port is not blocked on both remote computer and Parallels Access sides: