Hello Julian,
Please confirm that the password string enterd is at least 6 characters long and it contains numbers and letters.
Confirm that you had installed before the JDK enclosed in the 3rd Party ISO
For the sake of testing please disable the local firewall
# systemctl stop firewalld.service
# systemctl disable firewalld.service
Should the problem remain, please open a Support Case with us and we shall have a closer look.
Best Regards,
Andreas