You might see this error in the Intel® Quartus® Prime® Pro Edition Software version 18.0 and earlier when you open a Platform Designer system (.qsys file) created in version 18.1 or later.
The error occurs because the Intel Quartus Prime Pro Edition Software version 18.1 and later, supports the IPXACT 2014 format while earlier version support IPXACT 2009.
Platform Designer files are not backwards compatible, and should not be opened in older tool versions.
Full error message is as follows:
Error: Problem loading file <ip_name>.ip error was: javax.xml.bind.UnmarshalException: unexpected element (uri:"http://www.accellera.org/XMLSchema/IPXACT/1685-2014", local:"component"). Expected elements are ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,Error: The system could not be opened: <path_to_ip_file>/<ip_name>.ip
To avoid this error, do not open the Platform Designer systems created in the Intel Quartus Prime Pro Edition Software version 18.1 or later with version 18.0 or earlier.
The Intel Quartus Prime Pro Edition Software version 18.1 and later supports IPXACT 2009 & 2014 but generates files using IPXACT 2014.
The Intel Quartus Prime Pro Edition Software version 18.0 and earlier only supports IPXACT 2009.