It seems it is complaining that the version of npm installed is different than the one it supports, you have v8 and it is aiming for v6… but it is only a warning.
I had that in the past with other projects, try to bypass it with the flag --ignore-engines.
So delete your package-lock and node-sources and do npm i --ignore-engines and see if something changes.
How are you running the project? Try to manually start it first with npm run develop and not with another service (i.e. pm2).