(2) If you do not have access to the old computer for some reason, you are still able to deactivate the old computer. To do this you will need to visit www.adobe.com and sign in with your Adobe account. Click on Help & Support, Manage my account. Click on Plans and payment drop down at the top of the screen. Click on Activated devices. From there you have the option to sign yourself out of all other computers or devices. Once you have one or zero devices, you will be able to use Creative Cloud on another device.
Once you have deactivated other devices, you may need to Retry on the new device if you got an error message similar to this.