Can't install FA on remote server

Oooookay so, i’ve tried the git solution to deploy on my plesk server. Here is the result that my domain name show when i’m on his web page with node js launched :

/var/www/vhosts/vivactishealthcare.com/admin.vivactishealthcare.com/node_modules/express-jwt/lib/index.js:20
if (!options || !options.secret) throw new Error(‘secret should be set’);
^

Error: secret should be set
at module.exports (/var/www/vhosts/vivactishealthcare.com/admin.vivactishealthcare.com/node_modules/express-jwt/lib/index.js:20:42)
at Object. (/var/www/vhosts/vivactishealthcare.com/admin.vivactishealthcare.com/app.js:36:9)
at Module._compile (internal/modules/cjs/loader.js:774:30)
at Object.Module._extensions…js (internal/modules/cjs/loader.js:785:10)
at Module.load (internal/modules/cjs/loader.js:641:32)
at Function.Module._load (internal/modules/cjs/loader.js:556:12)
at Module.require (internal/modules/cjs/loader.js:681:19)
at Module.require (/usr/share/passenger/helper-scripts/node-loader.js:80:25)
at require (internal/modules/cjs/helpers.js:16:16)
at loadApplication (/usr/share/passenger/helper-scripts/node-loader.js:243:2)
at setupEnvironment (/usr/share/passenger/helper-scripts/node-loader.js:214:2)
at Object. (/usr/share/passenger/helper-scripts/node-loader.js:133:1)
at Module._compile (internal/modules/cjs/loader.js:774:30)
at Object.Module._extensions…js (internal/modules/cjs/loader.js:785:10)
at Module.load (internal/modules/cjs/loader.js:641:32)
at Function.Module._load (internal/modules/cjs/loader.js:556:12)
at Function.Module.runMain (internal/modules/cjs/loader.js:837:10)
at internal/main/run_main_module.js:17:11

Also, i have this error on the env configuration page (when FA send the new secret key etc) :

Access to XMLHttpRequest at ‘https://admin.vivactishealthcare.com/forest’ from origin ‘https://app.forestadmin.com’ has been blocked by CORS policy: Response to preflight request doesn’t pass access control check: No ‘Access-Control-Allow-Origin’ header is present on the requested resource.