Description
You may see this error message when you attempt to generate the Low Latency Ethernet 10G MAC IP core in the Quartus® II or Quartus Prime software.
Resolution
This problem can be resolved by setting the QSYS_ROOTDIR as a System Variable, and adding that variable to the System path statement. This is described in the Quartus Install Manual in the "Quartus Prime Environment Variables" section:
/content/dam/altera-www/global/en_US/pdfs/literature/manual/quartus_install.pdf
The following link includes some additional information on those variables and how to set them in Windows: