I've resolved my issue.

Unfortunately QB decided that RDS was no longer an option and pulled it from up without notification.

I cant vouch for other configurations but on POS v12 and QB Desktop v18 you will need to have a (non-running) copy of QuickBooks on the POS workstation.  Learn how to set it up by going to the POS Help and find the QuickBooks Financial Software Installation Options help screen.  On that screen you will find that you were using option 3 (RDS) but now you need to use option 2; QuickBooks Installed on Point of Sale Server Workstation and Another Network Workstation.  Pretty straightforward but a couple of gotchas:  you cant be running QuickBooks Desktop simultaneously on both computers (you only need to run it on the POS computer to set it up then close it), you want to have two different Admin logons for QuickBooks Desktop and you need to set QuickBooks Desktop into multi user mode ( https://quickbooks.intuit.com/learn-support/en-ca/apps-integrations/set-up-and-install-a-multi-user-... ) .

Took me about 2 hours with a little trial and error.

Good Luck!