Problem with yum and subscribe

Hello!

I am trying to install NVIDIA drivers according to http://www.advancedclustering.com/act_kb/installing-nvidia-drivers-rhel-centos-7/ see below:

yum -y update
yum -y groupinstall "GNOME Desktop" "Development Tools"
yum -y install kernel-devel

But when I type I got the following:

[root@Fatman ~]# yum -y update
Loaded plugins: langpacks, product-id, search-disabled-repos, subscription-
: manager
This system is not registered with an entitlement server. You can use subscription-manager to register.
There are no enabled repos.
Run "yum repolist all" to see the repos you have.
To enable Red Hat Subscription Management repositories:
subscription-manager repos --enable
To enable custom repositories:
yum-config-manager --enable
[root@Fatman ~]#

Here's something that does not work. I found https://access.redhat.com/discussions/3066851 where you can read the following:

First clean up everything - open a terminal and execute the following commands :

sudo subscription-manager remove --all
sudo subscription-manager unregister
sudo subscription-manager clean

Now re-register the system, attach the subscriptions - execute these commands :

sudo subscription-manager register
sudo subscription-manager refresh
sudo subscription-manager attach --auto

But I'm apparently not an subscriber even though I have reinstalled RHEL 7.4 a couple of times and registered.

[root@Fatman ~]# sudo subscription-manager remove --all
0 subscriptions removed at the server.
[root@Fatman ~]# sudo subscription-manager unregister
Unregistering from: subscription.rhsm.redhat.com:443/subscription
System has been unregistered.
[root@Fatman ~]# sudo subscription-manager clean
All local data removed
[root@Fatman ~]# sudo subscription-manager register
Registering to: subscription.rhsm.redhat.com:443/subscription
Username: myUserName
Password:
Invalid username or password. To create a login, please visit https://www.redhat.com/wapps/ugc/register.html
[root@Fatman ~]# sudo subscription-manager refresh
This system is not yet registered. Try 'subscription-manager register --help' for more information.
[root@Fatman ~]# sudo subscription-manager attach --auto
This system is not yet registered. Try 'subscription-manager register --help' for more information.
[root@Fatman ~]#

What is it that is wrong? And what am I doing wrong?

Thanks in advance and mvh:

Michae