Problem when logging into ERPNext with a user

I have created a user to test some Custom Doctypes that I have created. The user only has a permission created by me to have full control over the Custom Doctypes.

When I try to login to ERPNext with this user, the system displays a message that says I’m not allowed to access this page. In the Security Configuration section of the user, the User Type field is equal to System User, so that user must have access to the desktop.

EDITED: When I login to ERPNext, I can see that the indicator in the login form changes from blue to green and, a few seconds later, the page changes to the message box Not allowed

If you can post the errors you are getting in browser console, maybe someone can help

The instant I login, the page (and the browser console) are automatically refreshed to show the message box Not allowed, and I can not see last errors, but, for a few milliseconds, I can see there is at least one error related to the HTTP Status Code 403 (FORBIDDEN).