access denied - MySQL and NodeJS

Hi, I'm trying to run a NodeJS (Loopback) application which connects to a MySQL database. I can not get MySQL to allow me access, I always get the error: "access denied for user '[user]' @ 'localhost'. Does anyone have an idea why this may be happening? Try with different users, with the root user, with the user where the database is created, create users from cPanel and assign them to the base, but no way does it allow me access.