Converted it, but it still didn't work:
C:\WINDOWS\system32> cd "c:\Program Files\VMware\VMware OVF Tool"
c:\Program Files\VMware\VMware OVF Tool>ovftool.exe navappliance.ovf navappliancenew.ovf
Opening OVF source: navappliance.ovf
Opening OVF target: navappliancenew.ovf
Writing OVF package: navappliancenew.ovf
Transfer Completed
Warning:
- No manifest file found.
- Wrong file size specified in OVF descriptor for 'navappliance-disk001.vmdk' (specified: -1, actual 923340288).
- No supported manifest(sha1, sha256, sha512) entry found for: 'navappliance-disk001.vmdk'.
Completed successfully
c:\Program Files\VMware\VMware OVF Tool>
In EXSI: Line 16: Missing child element 'VirtualHardwareSection'.