@CFamilyPrinter,
Welcome to HP Forums, this is a great place to get support, find answers and tips.
Thank you for posting your query, I'll be more than glad to help you.
I understand that you are unable to scan to computer from your HP Officejet Pro 8600 Plus e-All-in-One Printer as you get a communication error when you try to enable scan to the computer on the network.
This issue could occur if the firewall is blocking the printer and you need to add it to the trusted list.
Let's go through a few steps to resolve this issue.
And here's the step by step guide for you in the link: Network Scanner Connection Error (Mac)
If the issue still persists, then you may need to update the firmware from the link: Firmware Update
Also, let us know the firewall that you are using on your computer.
Let me know how this works.
You have a good day ahead.
Rainbow23 - HP Support.