After several found i fixed the issue editing the <Portal_Server_root>\wps.properties
Inside this file you have to check the following parameters
ProfileName=<your profile name, e.g. wp_profile>
ProfileDirectory=<your profile directory, e.g. /opt/IBM/WebSphere/wp_profile>
to fix my issue i had to change the ProfileDirectory \ into /
i changet from
this fixed the issue.
I know WebSphere portal 7 is EOL but I'vent find anything on it so maybe this blogpost could be useful for someone in my same situation.