Hello, I assume you fixed this but I saw this post when I was looking to do the same thing in UniFi.
Assuming you have a HOME vlan (PC) and an IOT Vlan (PRINTER) set up.
Verify that you can ping the printer from your PC. If not, turn off your windows firewall and try. If that works, then you must add a rule to allow other networks through your PRIVATE NETWORK firewall. You can allow 192.168.0.0/16 for example. Then turn back on the firewall.
Now that you know you can ping (and get the reply) from the printer. Set the IP in UnifI console as static for the Printer.
Then add a printer using the IP address from the windows control panel and windows 10 is pretty good about finding setting up the drivers. (Or you can cheat and add the printer locally or be in same vlan to get the drivers installed so when you do the IP printer install they are already there.)
Then with the printer as static IP, that printer in you windows PC should work. Did for me.