The SELinux restricts binaries that can be used in ExecStart to paths that has system_u:object_r:bin_t:s0 attribute set. Typically those are /usr/bin /usr/sbin /usr/libexec /usr/local/bin directories.
You need to move the script into one of this directories or change selinux policy to allow systemd to use binaries in the desired location as:
chcon -R -t ...
As always, the issue is with the chair-keyboard interface...
So it appears that my project is based on java 13 and that my tomcat server was operating with java 8.
I reinstalled my server, put the correct jdk (instead of the previous jre) and now it's working. Now I only have to see why I can't access it from the network.
Thank you for your advices!
Through Terminal/SSH session, open the /var/packages/Tomcat7/target/src/conf/tomcat-users.xml file.
Ensure atleast below is available in that:
<user username="tomcat" password="s3cret" roles="manager-gui"/>
Under Package Center in the Diskstation, restart Tomcat service (...