This days implementing VPN solution is almost a daily task … I encountered a bug that has been around for some time now. If you deploy RRAS on Windows Server 2019 that is not DHCP server it does not request / reserve IP addresses from DHCP (that runs on some other server).
Everything works perfectly if you assign static range of IP addresses but I just want to manage VPN client IP addresses by using DHCP server.

In System log in Event viewer you will receive Event ID 20167 with information:
RoutingDomainID- {: No IP address is available to hand out to the dial-in client.

After a quick search I found the article on MS forums that states:

Add this registry entries to your VPN server and reboot it.

reg add “HKLM\SYSTEM\CurrentControlSet\Services\Dhcp” /v RequiredPrivileges /d “SeChangeNotifyPrivilege”\0″SeCreateGlobalPrivilege”\0″SeImpersonatePrivilege”\0 /t REG_MULTI_SZ /f

Hope it helps like it did in last five implementations I was working on recently.