We compiled simple Nios systems which work but once we add the ddr-emif component to our design it still compiles but the Nios software build tools can't find the processor to download the binary.
It should be working fine. I've opened by 18.1 and 19.0 many projects been created by 16.1 .
Can you please check the License files?
I will reach the license expert to find the reason.