Be sure you're signed in to Parallels Access on your mobile device. Tap Sign In at the bottom of the screen.
Be sure you are signed in to the Parallels Access agent on your computer. Click the Parallels Access icon in the menu bar or task bar on your computer and choose Sign In.
If you don't have a Parallels account, you can register for one using Parallels Access on your mobile device.
Be sure the Parallels Access agent on your computer is set to be accessible by clicking Turn On Access, if necessary. A green light indicates your computer is accessible.
If you're still unable to connect, try restarting your computer and your mobile device, and then try connecting again.