I have seen that error a bunch over the years and it tends to mean either the password is wrong or the user is not allowed to login from that IP. When you made the user did you do create user 'n8n'@'10.5.13.129' or something else?
You can double check the allowed locations with something like SELECT user,host FROM mysql.user;
Can you open a new post and complete the template provided? If you are seeing the exact same error message as the one in this post it will likely be down to the database not wanting to allow the user access.