Just maintain the correct path for both.

For me the command was,

C:/omnetpp/veins-master/sumo-launchd.py -vv -c 'C:/Program Files (x86)/Eclipse/Sumo/bin/sumo-gui.exe'

It is working fine. Please be aware while copying the path. I faced the same issue because while copying I missed the drive name. That's why the system thought it was a relative path.

Also, check the compatibility of Veins, INet, Omnet, Sumo