May I know 2012 AD server not available to deploy printer on 2019 server?
To deploy printer connections using Group Policy, the Active Directory Domain Services (AD DS) schema version must be at least Windows Server 2008.
1.Do they get the update when you run gpupdate /force?
2.Run gpresult /h report.html on the clients to check whether the GPO has been applied successfully
3.Have you tried log them off and log back on the computer?
4.Where did you configure this policy? Under user configuration or computer configuration?
I would highly recommend to check below 2 articles:
10 Common Problems Causing Group Policy To Not Apply - TechNet Articles - United States (English) - TechNet Wiki (microsoft.com)
Troubleshooting: Group Policy (GPO) Not Being Applied to Clients | Windows OS Hub (woshub.com)
Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.